Sydney South West Area Health Service v Stamoulis

CATCHWORDS: EVIDENCE - admissibility and relevancy - opinion evidence - expert evidence - whether trial judge erred in preferring the opinion of one expert to another where the former had greater expertise - whether trial judge impermissibly took into account own opinions on issues requiring expert testimony - effect of rules of court on admissibility of expert evidence and expert opinion evidence - whether evidence of expert materially interested in the proceedings is admissible. - CAUSATION - material increase in the risk - whether risk created by the tortfeasor came home - use of epidemiological and statistical evidence.

Civil Liability Act 2002 Civil Procedure Act 2005 LEGISLATION CITED: Evidence Act 1995 Supreme Court Rules 1970 Suitors' Fund Act 1951 Uniform Civil Procedure Rules 2005

Adelaide Stevedoring Co Ltd v Forst [1940] HCA 45; (1940) 64 CLR 558 Allianz Australia Insurance Ltd v GSF Australia Pty Ltd [2005] HCA 26; (2005) 221 CLR 568 ASIC v Rich [2005] NSWSC 149 Bendix Mintex Pty Ltd v Barnes (1997) 42 NSWLR 307 Betts v Whittingslowe [1945] HCA 31; (1945) 71 CLR 637 Blatch v Archer (1774) 1 Cowp 63; 98 ER 969 Boughey v The Queen [1986] HCA 29; (1986) 161 CLR 10 Briginshaw v Briginshaw [1938] HCA 34; (1938) 60 CLR 336 Chappel v Hart [1998] HCA 55; (1998) 195 CLR 232 Clark v Ryan [1960] HCA 42; (1960) 103 CLR 486 Collins Thomson v Clayton [2002] NSWSC 366 Derby & Co Ltd and Others v Weldon and Others, The Times, Nov 9, 1990 Dobler v Halverson [2007] NSWCA 335; (2007) 70 NSWLR 151 EMI Australia Ltd v BES [1970] 2 NSWR 238 Fernandez v Tubemakers of Australia Ltd [1975] 2 NSWLR 190 Festa v R [2001] HCA 72; (2001) 208 CLR 593 FGT Custodians Pty Ltd (formerly Feingold Partners Pty Ltd) v Fagenblat [2003] VSCA 33 Field v Leeds CC (2000) 32 HLR 618 Flavel v South Australia [2007] SASC 50; (2007) 96 SASR 505 Flounders v Millar [2007] NSWCA 238 Fortson Pty Ltd v Commonwealth Bank of Australia [2008] SASC 49; (2008) 100 SASR 162 Gett v Tabet [2009] NSWCA 76 In Re JS (a minor) [1980] 1 All ER 1061 James Hardie & Co v Roberts [1999] NSWCA 314; (1999) 47 NSWLR 425 Jones v Sutherland Shire Council [1979] 2 NSWLR 206 CASES CITED: Kirch Communication Pty Ltd v Gene Engineering Pty Ltd [2002] NSWSC 485 Li v R [2003] NSWCCA 290; (2003) 139 A Crim R 281 Luxton v Vines [1952] HCA 19; (1952) 85 CLR 352 Liverpool Roman Catholic Archdiocesen Trustees Inc v Goldberg (No 2) [2001] 1 WLR 2337 Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305; (2001) 52 NSWLR 705 March v Stramare (E & M H) Pty Ltd [1991] HCA 12; (1991) 171 CLR 506 Myers v Elman [1940] AC 282 National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) [1993] 2 Lloyd's Rep 68 National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) (No 1) [1995] 1 Lloyd's Rep 455 Payne v Crawford (1992) 3 Tas R 360 Polivitte Ltd v Commercial Union Assurance Co Plc [1987] 1 Lloyd's Rep 379 R (Factortame Ltd) v Secretary of State for Transport, Local Government and the Regions [2002] EWLA Civ 932 (No 2) [2003] QB 381 R v Mitchell (1997) 130 ACTR 48 Roads & Traffic Authority v Royal [2008] HCA 19; (2008) 82 ALJR 870 Rondel v Worsley [1969] 1 AC 191 Rufo v Hosking [2004] NSWCA 391; (2004) 61 NSWLR 678 Saunders v Adderley [1999] 1 WLR 884 Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; (2000) 49 NSWLR 262 Sherman v Nymboida Collieries Pty Ltd [1963] HCA 63; (1963) 109 CLR 580 State Government Insurance Commission v Laube (1984) 37 SASR 31 Strinic v Singh [2009] NSWCA 15 TC by his tutor Sabatino v The State of New South Wales [2001] NSWCA 380 Waterways Authority v Fitzgibbon [2005] HCA 57; (2005) 221 ALR 402 Weal v Bottom (1966) 40 ALJR 436 Whitehouse v Jordan [1981] 1 WLR 246 Workers' Compensation (Dust Diseases) Board v Veksans (1993) 32 NSWLR 221

TEXTS CITED: Cross on Evidence (loose-leaf), Lexis Nexis Au

PARTIES: Sydney South West Area Health Service (Appellant) Kristy Michelle Stamoulis (Respondent)

COUNSEL: P Menzies QC; C F Hodgson (Appellant) B M J Toomey QC; D R J Toomey (Respondent)

SOLICITORS: I V Knight, Crown Solicitor's Office (Appellant) McLaughlin & Riordan Solicitors (Respondent)

LOWER COURT JURISDICTION: Supreme Court

LOWER COURT DATE OF DECISION: 29 October 2008

LOWER COURT MEDIUM NEUTRAL CITATION: O'Gorman v Sydney South West Area Health Service [2008] NSWSC 1127

IN THE SUPREME COURT OF NEW SOUTH WALES COURT OF APPEAL CA 40401/08 SC 20239/08

BEAZLEY JA GILES JA IPP JA

24 JULY 2009 Sydney South West Area Health Service v Kristy Michelle Stamoulis Headnote FACTS

The appellant implements a State and Federal Government funded program that provides free breast screening mammograms. "BreastScreen NSW Sydney South West" ("BreastScreen") is one of the local services operated by the appellant. The respondent is the legal representative of the estate of the late Christine Ann O'Gorman. During her lifetime, Mrs O'Gorman brought proceedings against the appellant for damages for negligence. Mrs O'Gorman's claim arose out of a mammogram performed on her by BreastScreen on 23 February 2006.

On 2 and 3 March 2006, two radiologists (Drs Van Rooijen and Varnava) acting on behalf of BreastScreen, examined Mrs O'Gorman's mammogram and considered that it did not indicate anything untoward and did not recommend any further investigation. Following that mammogram, Mrs O'Gorman took no steps to investigate the possible existence of a cancer in her breast until 17 January 2007, when BreastScreen carried out a further mammogram. She was then diagnosed with having a carcinoma of the left breast. The carcinoma subsequently metastasised into Mrs O'Gorman's lungs and brain. After the trial, but before the hearing of the appeal, Mrs O'Gorman died.

At trial, Mrs O'Gorman contended that her 2006 mammogram displayed suspicious signs of the presence of a malignant mass in her left breast. Mrs O'Gorman's case alleged that the two radiologists were negligent in failing to recall her for further investigation and that this caused the metastasised tumours from which, at the time of the trial, Mrs O'Gorman was suffering.

The trial judge, Hoeben J found in favour of Mrs O'Gorman. His Honour assessed Mrs O'Gorman's damages in the sum of $405,990.15 and granted judgment in her favour against the appellant in this amount. On appeal, the appellant challenged the trial judge's findings as to negligence and causation. The respondent cross-appealed on the assessment of damages.

HELD allowing the appeal, ordering a re-trial on the issue of negligence and dismissing the cross-appeal

1. A mere material increase in the risk of injury followed by the eventuation of the risk in question is insufficient to establish causation. The plaintiff must establish that it was probable that the risk created by the tortfeasor came home. Flounders v Millar [2007] NSWCA 238 applied Gett v Tabet [2009] NSWCA 76 considered Workers' Compensation (Dust Diseases) Board v Veksans (1993) 32 NSWLR 221 considered Roads & Traffic Authority v Royal [2008] HCA 19; (2008) 82 ALJR 870 referred to Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; (2000) 49 NSWLR 262 referred to Bendix Mintex Pty Ltd v Barnes (1997) 42 NSWLR 307 referred to TC by his tutor Sabatino v The State of New South Wales [2001] NSWCA 380 referred to

2. There are dangers in applying evidence that tends to quantify possibilities mathematically. There are also dangers in applying epidemiological or statistical evidence in a mechanical way. It is overstating the position to say that, as an absolute proposition, the statistical fact that a particular proposition is true of the majority of persons cannot of itself amount to legal proof on the balance of probabilities that the proposition is true of any given individual. The matter is essentially one of degree. State Government Insurance Commission v Laube (1984) 37 SASR 31 considered Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; (2000) 49 NSWLR 262 referred to Re JS (a minor) [1980] 1 All ER 1061 referred to

3. Evidence of epidemiological studies is circumstantial evidence, which may, alone, or in combination with other evidence, establish causation in a specific case. The fact that experts do not infer causation on a balance of probabilities does not mean that a court may not. A finding of causal connection may be made even when the expert evidence does not rise above the possible; the question is always whether the evidence as a whole establishes causation on a balance of probabilities. Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; (2000) 49 NSWLR 262 applied Jones v Sutherland Shire Council [1979] 2 NSWLR 206 considered Fernandez v Tubemakers of Australia Ltd [1975] 2 NSWLR 190 considered

4. In this case there was a strong possibility that, had the radiologists detected the tumour, it would not have metastasised. The increased risk to Mrs O'Gorman as an individual made it more likely that the tumour would metastasise and the risk was increased to an extent that was not negligible. This evidence is significant and is sufficient to tip the scales from that of strong possibility to a finding that, on a balance of probabilities, the failure to detect the tumour led to the metastasis. Gett v Tabet [2009] NSWCA 76 distinguished

It was a matter for the trial judge to determine the differences in opinion between competing experts and to determine what weight should be attributed to their expertise, qualifications and experience. There was no substance in the argument that the trial judge should have preferred the opinion of expert because his qualifications, in some way, were greater than those of another.

The trial judge did not offend the principles informing judicial fact finding and the receipt and interpretation of expert evidence. In particular, the trial judge did not impermissibly take into account his own opinions requiring expert testimony. Strinic v Singh [2009] NSWCA 15 referred to

Although the effect of court rules is that expert witnesses owe a duty to the court, the content of that duty, and the powers of the court in enforcing that duty, are yet to be determined finally. The rules impose more stringent duties on expert witnesses than did the common law. The rules do not, however, render inadmissible expert evidence of witnesses who have an interest in the proceedings. National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) (No 1) [1993] 2 Lloyd's Rep 68 considered FGT Custodians Pty Ltd (formerly Feingold Partners Pty Ltd) v Fagenblat [2003] VSCA 33 referred to

The evidence of an expert is not inadmissible merely because he or she is materially interested in the proceedings. Such matters go to weight and not admissibility. The trial judge erred in deciding that the evidence of Drs Van Rooijen and Varnava was inadmissible on this basis. FGT Custodians Pty Ltd (formerly Feingold Partners Pty Ltd) v Fagenblat [2003] VSCA 33 referred to Fortson Pty Ltd v Commonwealth Bank of Australia [2008] SASC 49; (2008) 100 SASR 162 referred to Li v R [2003] NSWCCA 290; (2003) 139 A Crim R 281 referred to Field v Leeds CC (2000) 32 HLR 618; [1999] CPLR 833 referred to

In all the circumstances, Dr Varnava's disallowed evidence had the capacity to bring about a different result in the case.

IN THE SUPREME COURT OF NEW SOUTH WALES COURT OF APPEAL CA 40401/08 SC 20239/08

BEAZLEY JA GILES JA IPP JA

Sydney South West Area Health Service v Kristy Michelle Stamoulis

Judgment 1 BEAZLEY JA: I have had the benefit of reading in draft the judgments of Giles JA and Ipp JA. I agree that the appeal should be allowed for the reasons given by Ipp JA. I also agree substantially with the reasons of Giles JA. I wish only to make the following brief additional comments. 2 The first relates to the evidence of Professors Levi and Tattersall. At trial, the appellant accepted that the evidence of these two doctors related to the statistical chance that Mrs O'Gorman had of developing metastasised tumours. His Honour's finding in respect of their evidence was made on that basis. The appellant contended on appeal that their evidence was evidence of the statistical likelihood of a person with breast cancer developing metastasised tumours and was not evidence that related to the individual case of the respondent. 3 Giles JA and Ipp JA have expressed different views as to whether the appellant should now be permitted to take a different stance in respect of this evidence than was taken at trial. Overall, I am inclined to agree with Ipp JA that the appellant should not now be permitted to argue this issue differently from the trial. 4 The appellant conducted its case at trial on the basis that the decision in Rufo v Hosking [2004] NSWCA 391; (2004) 61 NSWLR 678 was good law and sought to have damages assessed on the basis of a loss of a chance, should it be found liable in negligence. In those circumstances, it suited its forensic purposes to treat the evidence as being directed to Mrs O'Gorman's individual statistical chance of developing metastasised tumours as that statistical chance was relatively low. Any damages would then reflect that low statistical chance. 5 Between the hearing at first instance and the appeal, this Court held in Gett v Tabet [2009] NSWCA 76 that Rufo should not be followed. The consequence for the appellant was that the forensic approach it took at first instance was to no avail. Whilst it was perfectly proper for the appellant to make forensic decisions in the conduct of its case, it should be bound by the way its case was conducted at trial. There are practical reasons why this is so. 6 Had the appellant not accepted that the evidence of Professors Levi and Tattersall related to Mrs O'Gorman's individual case, different submissions might have been made at trial. If the appellant had taken a different approach at trial, Mrs O'Gorman's legal representatives might have sought to adduce further evidence, including by way of cross-examination of the two medical experts. Giles JA has noted that the appellant's acceptance that the evidence related to Mrs O'Gorman personally only came in its final submissions. However, the Court does not know whether there was some earlier acknowledgement or tacit acceptance that that was so. Even had there been no earlier indication by the appellant of its position in relation to this evidence, the respondent might still have applied for leave to re-open to adduce further evidence from either or both Professor Levi and Professor Tattersall. 7 Save for the above comments, I agree with their Honour's respective reasons in relation to causation. 8 The second matter upon which I wish to comment relates to the rejection of certain of the evidence of Drs Varnava and Van Rooijen. The trial judge said that he rejected the evidence of these two witnesses for a number of reasons including that "the evidence was in the nature of expert evidence and had not been served in accordance with the rules". As Ipp JA observes, the trial judge did not state which aspects of the Uniform Civil Procedure Rules 2005 (UCPR) he relied upon to reject this evidence. 9 In my opinion, it is unlikely that his Honour's concern was with service of the reports. It would not have made sense for his Honour to have been concerned with this, first, because he had permitted the matter to proceed urgently and without strict compliance with the rules; secondly, because the evidence of the two doctors had, in any event, been provided by way of report; and thirdly, because the service of expert reports was subject to his Honour's direction, as I explain below. 10 The question arises then as to what rules his Honour had in mind. Expert evidence is governed by UCPR, Pt 31. Pursuant to r 31.36(1), a person commencing a professional negligence claim must file an expert's report with the statement of claim. The court may also give directions as to the expert evidence to be adduced at trial: r 31.36(4). Directions may be sought, inter alia, by way of notice of motion: r 31.36(5). Rule 31.36(6) then provides, relevantly: "(6) Unless the court otherwise orders, no party may adduce any expert evidence at trial unless the evidence:

(a) has been filed and served under subrule (1) …or (b) has been served pursuant to directions given under subrule (4)." 11 His Honour could have given directions pursuant to subrule (6) during the course of the trial that the existing reports be treated as expert reports. It is unlikely, given that the manner in which the trial had proceeded, that his Honour would have been churlish about no notice of motion having been filed under subrule (5) seeking directions in respect of the reports. In any event, he had power to dispense with the requirements of that rule (and any rule) under the Civil Procedure Act, s 14. It is likely, in my opinion, that his Honour would have been concerned with matters of substance insofar as non-compliance with rules of court was concerned. 12 One of the significant requirements of the rules is that experts must agree to be bound by the expert witness code of conduct: UCPR, r 31.23 and Sch 7. Initially, I thought that it was likely that his Honour was concerned that these doctors had not provided reports that complied with the rules relating to the code of conduct. Whilst I consider that was likely, it is also possible that his Honour had other rules in mind. For example, there may have been an experts' conference in which the two doctors had not engaged: see UCPR, r 31.24. I should indicate, however, that the evidence does not reveal whether or not there was an experts' conference. 13 His Honour's reference could possibly have been directed to the fact that concurrent evidence had been given by Associate Professor Osborne and Dr Kitchener: see UCPR, r 31.35, on the issues on which the evidence of Drs Varnava and Van Rooijen was relevant, although it has to be recognised that the language used by his Honour was not apt to cover this possibility. His Honour may, however, have been using very general language to cover the range of rules that relate to expert reports. 14 The fact that there are a number of possibilities as to which rules his Honour was referring to reinforces the view expressed by Ipp JA that this aspect of his Honour's ruling is unclear. This is relevant because unless the basis for the ruling is known, it is not possible to determine whether his Honour erred in the exercise of the discretion that is conferred by the rules in respect of the admission of expert evidence. 15 That leads me to another point. Senior counsel for the respondent submitted that because the reports of Drs Varnava and Van Rooijen did not include a statement that each agreed to be bound by the code of conduct, the reports were not admissible. That submission must be rejected. UCPR, r 31.23(3) provides that: " Unless the court otherwise orders , an expert's report may not be admitted in evidence unless the report contains an acknowledgment by the expert witness by whom it was prepared that he or she has read the code of conduct and agrees to be bound by it." (Emphasis added) 16 His Honour could have made an order under this subrule that the reports be admitted, notwithstanding that they did not contain the statement relating to the code of conduct. That would have been an appropriate order to make in this case, given the urgency with which the trial proceeded. In any event, the doctors could have made the relevant statement as to the code of conduct in the witness box. 17 The real question therefore becomes whether Drs Varnava and Van Rooijen could give expert evidence. It is apparent from his Honour's comments during the course of the trial that he considered that they could not give expert evidence, effectively in their own cause, their examination of the mammograms being at the heart of the negligence claim against the appellant. For the reasons given by Ipp JA, that is not correct. What weight his Honour might have given to the evidence is a separate matter. However, weight does not affect admissibility. 18 I agree with the orders proposed by Ipp JA. 19 GILES JA: The issues in the appeal and cross-appeal are described in the reasons of Ipp JA, which I have had the considerable benefit of reading in draft. 20 I agree that the challenges to the trial judge's factual findings concerning the increase in size of the mass should not succeed and that the cross-appeal on damages should be dismissed. In these respects I agree with the reasons given by Ipp JA and do not wish to add anything. 21 I agree also that the trial judge's finding of causation should be upheld, and that the trial judge was in error in rejecting the evidence of Drs Van Rooijen and Varnava and a new trial on the issue of negligence should be ordered. In these respects I generally agree with his Honour's reasons, but subject to the following observations.

Causation 22 The trial judge posed the question of "the difference a diagnosis in 2006 would have made to the plaintiff's outcome". He found that Mrs O'Gorman would have "undergone all investigations which were recommended to her", as I understand it meaning also treatment. His Honour said, the survival rates being with treatment - " [137] There was no material difference between the evidence of Professors Levi and Tattersall as to the survival rates attached to a diagnosis of breast cancer in March 2006, rather than January 2007, and the percentage likelihood of metastasisation. The effect of their combined opinion is that the risk of the plaintiff's breast cancer metastasising between March 2006 and January 2007 increased by approximately 10%. That figure was agreed by the parties in their written submissions. Thereafter, the parties dramatically diverge in their approach." 23 As Ipp JA has described, the 10 per cent increase in risk was derived from the opinions that, had the mass been detected and treated immediately after the mammogram of 23 February 2006, there was a 38 per cent chance of the metastatic tumours nonetheless developing, and that the equivalent figure as at 17 January 2007 was 42 per cent. There was mathematically an approximate 10 per cent increase in the risk of metastasisation. 24 The defendant submitted to the trial judge, relying on Rufo v Hosking [2004] NSWCA 391; (2004) 61 NSWLR 678 and Dobler v Halverson [2007] NSWCA 335; (2007) 70 NSWLR 151, that there should be found a 10 per cent lost chance of a better outcome caused by the delay in diagnosis; implicitly, therefore the plaintiff should recover only 10 per cent of the assessed damages. The plaintiff submitted, relying in particular on what was said by McHugh J in Chappell v Hart [1998] HCA 55; (1998) 195 CLR 232 at [27], that the delay in diagnosis caused the metastatic tumours because there was a 10 per cent increase in the risk of those tumours developing and that risk eventuated; implicitly, therefore the plaintiff should recover the full amount of the assessed damages. 25 The trial judge noted that neither party referred to ss 5D and 5E of the Civil Liability Act 2002. He accepted that these provisions were in accord with common law principles. After reference to other cases, he expressed his conclusion - "[150] The submission put on behalf of the plaintiff should be accepted. The evidence clearly supports the application of the causation principle stated by McHugh J in Chappel v Hart . The uncontradicted evidence of Professors Levi and Tattersall is that the delay in diagnosis increased the risk of metastasisation by 10%. This was not a case where metastasisation was likely in any event and the plaintiff had merely lost the chance of a better outcome. The events which occurred, ie the development of tumours in the plaintiff's lungs and brain, occurred within the very area of risk which had been increased by the delay in diagnosis.

[151] I find that there is no scope for the application of the principle in Rufo v Hosking and that the plaintiff has established that the defendant's conduct caused the tumours from which she now suffers in her lungs and brain." 26 Dobler v Halverson did not endorse Rufo v Hosking, and Rufo v Hosking has since not been followed: Gett v Tabet [2009] NSWCA 76. The appellant did not, other than by a formal submission, maintain on appeal that the recovery should be on the basis of loss of a chance of a better outcome. 27 The appellant's position on appeal was that Mrs O'Gorman could recover nothing, because the statistical increase in risk from 38 per cent to 42 per cent did not prove that the metastasisation she experienced was caused by the delay in diagnosis. Mrs O'Gorman might have been one of the statistical 38 per cent. There was an increase in risk, but increase in risk was not enough for causation and she might also have been one of the 42 per cent. A 42 per cent statistical risk was still less than a probability. Thus it was not shown that the delay in diagnosis had any effect on the progression of Mrs O'Gorman's cancer as at February 2006 to the metastasisation she experienced. 28 The appellant submitted that the present case was on all fours with Gett v Tabet. As Ipp JA has explained, that is not so. The plaintiff in Gett v Tabet failed to prove causation because whether the outcome would have been better had the CT scan been ordered on 13 January was no more than speculative. The Court endorsed at [254] that, while material increase in risk was not to be equated with material contribution to the injury, causation would be proved if the plaintiff established "that it was probable that the risk created by the tortfeasor came home". The plaintiff in Gett v Tabet did not. Whether Mrs O'Gorman did was the issue in the present case. 29 Language of the risk coming home was used by Mason P in Bendix Mintex Pty Ltd v Barnes (1997) 42 NSWLR 307, in the observation at 318 that a party who negligently exposes a plaintiff to a risk of injury will not be liable "unless the plaintiff can persuade the trier of fact that it was probable that the risk came home". The influential discussion, by Spigelman CJ (with whom Davies AJA agreed) in Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; (2000) 49 NSWLR 262 used and explained the similar language of the risk eventuating. Speaking of the statement by McHugh JA in Chappel v Hart at [27] that "[i]f a wrongful act or omission results in an increased risk of injury to the plaintiff and that risk eventuates, the defendant's conduct has materially contributed to the injury that the plaintiff suffers whether or not other factors also contributed to that injury occurring", the Chief Justice said - " [107] The starting point of McHugh J's analysis was that it had been established on the balance of probabilities that the conduct did create or increase the risk of injury, 'and that risk had eventuated'.

[108] This starting point is the very matter in issue in the present case. Was there evidence on the basis of which the trial judge could conclude, on the balance of probabilities, that there was an increased risk of injury and that that risk had 'eventuated' in the specific disease of the Respondent?

[109] If there was such evidence then, to use the words of both Gaudron J (at [31]) and Callinan J (at [128]), the tribunal of fact was 'entitled' to find that the conduct which increased risk, materially contributed to the injury - entitled, but not, of course, required to so find.

[118] The issue in the present case is whether an increased risk did cause or materially contribute to the injury actually suffered.

[119] There is a tension between the suggestion that any increased risk is sufficient to constitute a 'material contribution', and the clear line of authority that a mere possibility is not sufficient to establish causation for legal purposes. The latter is too well established to be qualified by the former. The reconciliation between the two kinds of references is to be found in the fact that, as in Chappel v Hart and in the cases that suggest the former, the actual risk had materialised. The 'possibility' or 'risk' that X might cause Y had in fact eventuated, not in the sense that X happened and Y had also happened, but that it was undisputed that Y had happened because of X.

[120] The epidemiological evidence in the present case can be expressed in terms of 'increased risk'. However, in its application to determining causation in the specific case of the Respondent that evidence never rises above the level of a possibility. Whether or not the increased risk 'eventuated', is the issue which must be determined. … " 30 That the risk "eventuated" did not mean simply that the plaintiff suffered the injury. If that were so, the small increased risk of renal cancer indicated by most of the epidemiological studies in Bendix Mintex Pty Ltd v Barnes plus the contraction of renal cancer would have established causation. The language of "coming home", albeit imprecise, may better convey the requirement that on the probabilities the injury was suffered because of the increase in risk. 31 It could be found that the 10 per cent increase in risk came home if it were established on the probabilities that Mrs O'Gorman was more than one of the statistical 38 per cent, and was a person for whom the progression from breast cancer to metastasised tumours was affected by the increase in risk. The risk to her as an individual, as distinct from a member of a statistical cohort, would have materially increased, and there would have been a material contribution to the progression of her cancer to the metastatisation. Hence the respondent's submission that the trial judge found at his [137] set out above that the approximate 10 per cent increase was specific to Mrs O'Gorman. 32 Such a finding could have been because of the evidence, or because of concession in the conduct of the defendant's case. 33 I do not think it was because of the evidence. Professors Levi and Tattersall expressed statistical opinions, not referable to Mrs O'Gorman in particular. While the plaintiff's submissions to the trial judge were in terms of "the plaintiff's risk of developing metastases", and the defendant's submissions did not take issue with the injection of the plaintiff as an individual, this application to the plaintiff of the figures may not have been a conscious step to the plaintiff's particular susceptibility. It was not a step founded on evidence. The trial judge's finding at [137] may not have consciously taken that step. 34 That in the conduct of the case at trial the defendant nonetheless conceded the application of the figures as a step to the plaintiff's particular susceptibility is, however, indicated by its loss of a chance approach. That approach accepted the 10 per cent increase in risk to the plaintiff, no doubt deliberately in the hope that the loss of a chance approach would greatly reduce damages. So before the trial judge the defendant's submissions included that if it was negligent "it affected arguably the outcome", but only as to the loss of a 10 per cent chance, and as Ipp JA has noted counsel accepted on appeal that the submissions involved that the risk to the plaintiff of metastasisation increased. 35 It does not follow that the appellant should not be permitted to take on appeal the position earlier described. So far as there was concession in the conduct of the trial, it appears to have been in submissions. We were not taken to anything which to my mind would work an injustice on the respondent if, the loss of a chance approach being unavailable since Gett v Tabet, the appellant were permitted to resort to other well-traversed principles of causation. 36 I go then to whether it should otherwise be found that the 10 per cent increase in risk came home. While the trial judge's reference to the cases included the Chief Justice's identification, in Seltsam Pty Ltd v McGuiness, of the question of whether there was evidence on the basis of which it could be concluded on the probabilities "that there was an increased risk of injury and that that risk had 'eventuated'", his Honour's explanation at [150]-[151] for his conclusion was (with respect) rather scanty. His Honour may have taken up a concession that the delay in diagnosis increased the risk to the plaintiff of metastasisation by 10 per cent. If he did not, the reasoning did not go further than that the development of the tumours was within the area of risk increased by the delay in diagnosis. 37 Ipp JA has fully referred to the authorities, and I respectfully and gratefully draw on what he has said. An increase in risk gives rise to a possibility of causation, but the possibility does not of itself make out causation. It may be that in particular circumstances the increase in risk will suffice for satisfaction, on the balance of probabilities, that the increase in risk came home, see Seltsam Pty Ltd v McGuiness at [89] and [153] and Ipp JA's example of a statistical increase in risk from 1 per cent to 99 per cent. And where there is evidence such as that given by Professors Levi and Tattersall, it can be taken into account together with other matters as "strands in the cable", a method of reasoning well established in the law. 38 It is necessary to recall that causation in law is not the same as scientific causation. It is addressed in order to attribute legal responsibility. The balance of probabilities is a departure from scientific certainty, and there is causation if there is material contribution. So in March v E & MH Stramare Pty Ltd [1991] HCA 12; (1991) 171 CLR 506 Mason CJ said at 509 - "In philosophy and science, the concept of causation has been developed in the context of explaining phenomena by reference to the relationship between conditions and occurrences. In law, on the other hand, problems of causation arise in the context of ascertaining or apportioning legal responsibility for a given occurrence. The law does not accept John Stuart Mill's definition of cause as the sum of the conditions which are jointly sufficient to produce it. Thus, at law, a person may be responsible for damage when his or her wrongful conduct is one of a number of conditions sufficient to produce that damage: see McLean v Bell , per Lord Wright; Sherman v Nymboida Collieries Pty Ltd [1963] HCA 63; (1963) 109 CLR 580, per Windeyer J." (footnotes omitted) 39 In March v E & MH Stramare Pty Ltd the Chief Justice referred at 515-519 to applying common sense to the facts of each particular case, and to the role of value judgments and the infusion of policy considerations. McHugh J in that case questioned the appeal to common sense, see also Allianz Australia Insurance Ltd v GSF Australia Pty Ltd [2005] HCA 26; (2005) 221 CLR 568 at [97] per Gummow, Hayne and Heydon JJ. The point remains that, in the absence of scientific clarity, causation may be found in arriving at legal responsibility by inference and with evaluative judgment, provided that actual satisfaction is reached and that, as was made clear in Travel Compensation Fund v Tambree [2005] HCA 69; (2005) 224 CLR 627, the finding is in accordance with principle and not a "value judgment at large" (per Gleeson CJ at [29]). 40 It is here that reference may be made to s 5D of the Civil Liability Act, which applied in this case. It relevantly provides - " 5D General principles

(1) A determination that negligence caused particular harm comprises the following elements:

(a) that the negligence was a necessary condition of the occurrence of the harm ( factual causation ), and

(b) that it is appropriate for the scope of the negligent person's liability to extend to the harm so caused ( scope of liability ).

(2) In determining in an exceptional case, in accordance with established principles, whether negligence that cannot be established as a necessary condition of the occurrence of harm should be accepted as establishing factual causation, the court is to consider (amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party.

(4) For the purpose of determining the scope of liability, the court is to consider (amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party." 41 Section 5D enshrines evaluative judgments in a determination that negligence caused particular harm, those of appropriateness for the scope of liability to extend to the harm for the occurrence of which the negligence was a necessary condition (s 5D(1)(b)) and of whether and why responsibility for the harm should be imposed on the negligent party (s 5D(2), (4)). It was not mentioned in argument, but underlines the common law principles to which I have referred. 42 As the trial judge said, Mrs O'Gorman's development of metastatic tumours was within the area of risk increased by the delay in diagnosis. It can not be said with anything approaching certainty that Mrs O'Gorman would not have developed the tumours in any event. But, albeit on a statistical basis, it can be said that the risk of her doing so was increased, and she was brought materially closer to the point where (also statistically) there was a likelihood (in the sense of a "substantial - a real and not remote - chance regardless of whether it is less or more than 50 per cent": Boughey v The Queen [1986] HCA 29; (1986) 161 CLR 10 at 21) that a tumour or tumours would develop.

43 One should have in mind that, in a case such as the present, medical science may not enable a plaintiff to point to a more direct connection than that provided by epidemiological studies (although gene technology may in the future enable more to be said). Rich ACJ remarked in Adelaide Stevedoring Co Ltd v Forst [1940] HCA 45; (1940) 64 CLR 558 at 564 that "while science presents us with no more than a blank negation, we can only await its positive results and in the meantime act on our own intuitive inferences". At least since Blatch v Archer (1774) 1 Cowp 63; 98 ER 969 the law has weighed evidence according to the power of one side to produce and the other side to contradict, and has not been indulgent to a (legal) wrongdoer. When the 10 per cent increase in risk, much more than the small risk in Seltsam Pty Ltd v McGuiness, took Mrs O'Gorman to likelihood in the sense earlier stated, for the purposes of legal responsibility I consider that on the balance of probabilities the increase in risk materially contributed to, and so caused, the development of the metastatic tumours.

Admission of evidence 44 Ipp JA has fully described the evidence in question, and the manner with which it was dealt at the trial. It is unfortunate that there was not a little more quiet calm deliberation, with the assistance of submissions from counsel. There is no doubt that the trial judge took an initial firm reaction, but the defendant's counsel could have been more forthright in exposing and arguing for admissibility; and counsel then appearing for the plaintiff could have contributed, since apart from a duty to assist the Court it is unlikely to be in the client's interest to stand by when a favourable but unsound ruling is given, without explication of the true basis of objection and deflection of the judge from error. Success at trial may be taken away on appeal. 45 I respectfully share Ipp JA's understanding that the trial judge rejected the evidence because he considered that the doctors were not giving evidence of what they did and thought at the time, and were precluded from giving expert evidence by their involvement at the time. It may be that, as evidence of practice, some at least of the rejected evidence was admissible, but the greater difficulty lies in the rejection of the evidence as expert evidence. 46 So far as the rejection may have been because what each doctor said "should have been dealt with as an expert report and it hasn't been", words used in relation to the statement of Dr Stephen, in my view his Honour did not mean the rules as to timely service. Rather, his Honour meant the requirement under the rules that an expert comply with the Code of Conduct under Pt 31 r 23. The essence of the trial judge's view was that the doctors' involvement at the time made their expert opinions unreliable, and therefore inadmissible, and compliance with the Code of Conduct went to reliability. There is no indication that, in the circumstances in which the trial was conducted, failure in timely service of the statements was of concern to the plaintiff. It will be noted that when the trial judge said, in [65] of his reasons, that Dr Van Rooijen's statement "had not been served in accordance with the rules", what followed was concerned with its reliability. 47 I agree with what Ipp JA has said concerning admissibility notwithstanding that the doctors may have been regarded as having an interest in the result in the proceedings. It can not be assumed that the doctors would have been unable to subscribe to the Code of Conduct had that been squarely raised. 48 A substantial wrong or miscarriage of justice was occasioned by the rejection of Dr Varnava's evidence, at the least, and there should be a new trial as to negligence. 49 I do not understand the trial judge to have rejected the evidence of either of the doctors in the exercise of the discretion under s 135 of the Evidence Act 1995, but if he did the discretion miscarried because there was no comparative analysis of probative value and danger of unfair prejudice or other of the factors in that provision. Indeed, that is one reason for concluding that s 135 was not in his Honour's mind, and his references to unfairness and unfairness to the plaintiff were in my reading of the transcript and judgment restatements of the unreliability he saw in the doctors' evidence. 50 Orders 51 I agree with the orders proposed by Ipp JA. 52 IPP JA:

The claim against the appellant and the decision of the trial judge 53 The appellant, the Sydney South West Area Health Service, implements a State and Federal Government funded program that provides free breast screening mammograms. The appellant's principal aim is to reduce the amount of illness and death associated with breast cancer through the early detection of the disease. It has a network of eight local services operating independently of each other in New South Wales. "BreastScreen NSW Sydney South West" ("BreastScreen") is one of the local services operated by the appellant. In these reasons, the appellant and BreastScreen are referred to interchangeably. 54 The respondent is the legal representative of the estate of the late Christine Ann O'Gorman. During her lifetime, Mrs O'Gorman brought proceedings against the appellant for damages for negligence. Mrs O'Gorman's claim arose out of a mammogram performed on her by BreastScreen on 23 February 2006. 55 On 2 and 3 March 2006, two radiologists, Drs Van Rooijen and Varnava, acting on behalf of BreastScreen, examined Mrs O'Gorman's 23 February 2006 mammogram. They considered that the mammogram did not indicate anything untoward and did not recommend any further investigation. It was not in dispute that the appellant is vicariously liable for the conduct of the two radiologists. 56 Before the trial judge, Hoeben J, Mrs O'Gorman contended that the 2006 mammogram displayed suspicious signs of the presence of a malignant mass in her left breast. Mrs O'Gorman's case was that, following the inspection of the 2006 mammogram, the two radiologists were negligent in failing to recall her for further investigation. 57 After the 2006 mammogram, Mrs O'Gorman took no steps to investigate the possible existence of a cancer in her breast until 17 January 2007, when BreastScreen carried out a further mammogram. She was then diagnosed with having a carcinoma of the left breast. 58 The carcinoma subsequently metastasised into Mrs O'Gorman's lungs and brain. After the trial, but before the hearing of the appeal, Mrs O'Gorman died. 59 Hoeben J found in favour of Mrs O'Gorman. That is, his Honour found that Drs Van Rooijen and Varnava were negligent as Mrs O'Gorman alleged and that the appellant was vicariously liable for their negligence. 60 The negligence as found involved the casual acts of negligence of the two radiologists in question, not a system of work. The respondent does not now assert a case based on a negligent system. 61 Hoeben J found further that the negligence of Drs Van Rooijen and Varnava caused the metastasised tumours from which, at the time of the trial, Mrs O'Gorman was suffering. His Honour assessed Mrs O'Gorman's damages in the sum of $405,990.15 and granted judgment in her favour against the appellant in this amount. 62 By this appeal, the appellant challenges his Honour's findings as to negligence and causation. The respondent cross-appeals on the assessment of damages. 63 The appellant's grounds of appeal fall into three main categories: (a) Challenges to the factual finding made by his Honour that the posterior mass depicted in the 2006 mammogram had significantly increased in size since 2004. These challenges may in turn be divided into three sub-categories, namely:

(i) The argument that his Honour erred in not preferring the opinion of Associate Professor Osborne (the expert called by the appellant) to Mrs O'Gorman's expert (Dr Kitchener) on the ground that Associate Professor Osborne had greater expertise.

(ii) The argument that his Honour erred in deriving support for his preference for Dr Kitchener's opinions from the evidence of Professor Levi and Dr Varnava.

(iii) The argument that, in preferring Dr Kitchener, his Honour impermissibly took into account his own opinions on issues requiring expert testimony.

(b) Submissions that his Honour erred in finding that the failure to recall Mrs O'Gorman for further examination caused the tumours that metastasised.

(c) Submissions that his Honour wrongly disallowed expert evidence by Drs Van Rooijen and Varnava that tended to justify their conduct.

The duty of care owed by the appellant 64 The mammograms BreastScreen carried out on Mrs O'Gorman were "screening" mammograms. A screening mammogram is a procedure designed to detect unsuspected lesions in asymptomatic "well" women. Hoeben J observed that, with screening mammograms, the emphasis is on mass population screening to reduce overall mortality and morbidity. The appellant provides recall for further tests when needed, as well as recall for routine screening at recommended intervals. 65 A screening mammogram is to be contrasted with a diagnostic mammogram. A diagnostic mammogram is used for diagnosing breast changes or abnormalities that may have been detected through breast self-examination or clinical examination. With a diagnostic mammogram the emphasis is on individual benefits. In an unchallenged finding Hoeben J accepted that there was a proper distinction to be drawn between the two kinds of mammograms. 66 Taking into account the differences between the two procedures, Hoeben J held that the appellant was obliged (at [107]): "to provide that level of care and skill in the interpretation of mammograms to be expected from a reasonably competent radiologist in the context of a mammogram screening program."

This finding was not challenged. 67 Thus, as his Honour held, it was necessary for Mrs O'Gorman to establish that there were suspicious features in the 2006 mammogram which sufficiently raised the possibility of malignancy to have required the two radiologists in question to recall her for further investigation. Mrs O'Gorman relied in this regard particularly on changes she contended should have been detected in the 2006 mammogram when compared with the mammograms carried out in 2002 and 2004. BreastScreen's practice at the relevant time 68 At the time of the 2006 mammogram BreastScreen's practice, in carrying out mammograms, was to take four to six films. These involved different views of each breast. The films were taken to a viewing room where a viewing machine would be loaded with the current mammograph films that were to be examined. The films would be placed on the top row. If available, comparison mammograph films previously taken were placed on the bottom row. Usually, these would be films taken four years previously. A light at the rear of the viewing machine illuminated the films. The viewing radiologist would be able to see the relevant films by scrolling across the screen of the viewing machine. 69 Two radiologists would always view the mammogram films. Each would do so separately and independently and make his or her own assessment. In doing so, neither had access to the assessment of the other. If the two assessments coincided, the recommendation by both was followed. If a disagreement arose, a third radiologist would read the films and the decision of the majority would be followed.

The Critical Factual Issue 70 Although a considerable amount of expert evidence, ranging over many issues, was given, the dispute between the parties' respective expert witnesses crystallised into one principal issue, described by Hoeben J as "a matter of fundamental importance at the trial". That issue was whether an area in the 2006 mammogram (to which all at the trial referred to as "the mass") had increased significantly in size when compared to mammograms that BreastScreen had performed on Mrs O'Gorman in 2002 and 2004. 71 Either the 2002 or 2004 mammograms were used as a comparator as it was common ground that there had been no material change in the size of the mass between 2002 and 2004. 72 The principal expert on whom Mrs O'Gorman relied was Dr Kitchener. BreastScreen, principally, relied on the expert testimony of Associate Professor Osborne. 73 Dr Kitchener identified aspects of the 2006 mammogram that gave rise to suspicions that a malignancy was present. As Hoeben J observed (at [112]), these were: "(a) A doubling in the size of the mass. (b) The partially indistinct margins of the mass. (c) The increase in size of the posteromedial band. (d) The presence of an anterior band. (e) The presence of calcification within the mass as well as within the bands. (f) Some lobulation laterally to the mass." 74 According to Dr Kitchener, the doubling in the size of the mass in the 2006 mammogram, when compared to the 2002 or 2004 mammograms, alone was sufficient to require the recall of Mrs O'Gorman. Dr Kitchener was of the opinion that the increase in size of the mass, alone, gave rise to a real suspicion that a cancer was present. 75 The other features Dr Kitchener identified were - according to him - not individually decisive. In his opinion, however, their total effect indicated that the 2006 mammogram displayed suspicious signs of malignancy. 76 Associate Professor Osborne, in essence, was of the opinion that all the potentially suspicious aspects of the 2006 mammogram identified by Dr Kitchener (except the increase in the size of the mass) were capable of a benign interpretation. Hoeben J pointed out in this regard (at [113]): "Associate Professor Osborne gave evidence in relation to all of those matters (except the increase in the size of the mass) to the effect that such signs were equivocal and were still consistent with a diagnosis of benign breast fibro-cystic changes. At no time did he concede that the calcification was suspicious in appearance." 77 Associate Professor Osborne acknowledged, however, that if the mass had approximately doubled in size as Dr Kitchener said, that would be a suspicious sign requiring Mrs O'Gorman's recall. His opinion in this regard is encapsulated in the following statement he made when giving oral evidence: "If there has been a significant increase in size, in other words, if there has been significant change then it is the change that necessitates - that would warrant the recall." 78 Later, he repeated that if the 2006 mammogram had indicated a "significant change in size" Mrs O'Gorman should have been recalled. 79 But, while Dr Kitchener was of the opinion that a significant increase in size (an approximate doubling) had occurred, Associate Professor Osborne differed. Associate Professor Osborne was of the opinion that the mass in 2006 was approximately the same size as it had been in 2004, although it was denser in appearance. He said that the mass depicted in the 2006 mammogram, when compared with either the 2004 or 2002 mammograms, was consistent with a benign cyst. Hoeben J noted that Associate Professor Osborne's position was that "there had not been any increase in size beyond what he described as marginal". 80 According to Hoeben J, this was the most obvious point of difference between the two doctors and became a decisive consideration on the question of breach. The parties did not challenge this approach. 81 His Honour preferred the opinion expressed by Dr Kitchener and rejected that of Associate Professor Osborne. This finding led inevitably to the further finding that Dr Van Rooijen and Dr Varnava had breached the duty of care that each owed Mrs O'Gorman. 82 The appellant's arguments, save in regard to the issue of causation, bore directly or indirectly on his Honour's finding that the 2006 mammogram indicated that the mass had increased significantly in size.

The relative expertise of Dr Kitchener and Associate Professor Osborne 83 The appellant submitted that Associate Professor Osborne had far greater expertise than Dr Kitchener in the reading of mammograms. The appellant submitted that Hoeben J erred in failing to pay due weight to this factor and should not have accepted the opinion of Dr Kitchener "who was much more a generalist than a specialist in this field". 84 Hoeben J dealt with this issue as follows (at [73]): "The defendant submitted that more weight should be given to the opinion of Associate Professor Osborne because he had greater experience in mammographic screening given his senior position with BreastScreen Queensland. While I accept that Associate Professor Osborne had more experience with the procedures and protocols followed by the BreastScreen organisation throughout Australia, I do not find that Associate Professor Osborne's expertise in the interpretation of mammograms and ultrasounds was any greater than that of Dr Kitchener. As is clear from the curricula vitae of both doctors, each is an experienced and highly qualified radiologist with a particular interest in breast imaging. The resolution of their conflict of opinion cannot be achieved by reference to any superior expertise on the part of either of them." 85 According to Associate Professor Osborne's curriculum vitae he has "sub-specialised for the past 20 years in women's imaging, and for the past decade in breast imaging and procedures". He has formal qualifications in assessment. He has organised training courses for radiologists in breast screening in Australia and other parts of the world. He has had considerable practical experience in assessing breast screening, this being part of his daily practice. In addition, for many years he has lectured and taught in the field of breast screening. 86 Dr Kitchener, as well, is a vastly experienced radiologist. He, too, has had considerable practical experience in medical imaging, particularly in regard to mammography. He has been concerned in the introduction of various mammography ultrasound techniques into clinical practice in Australia and has spoken widely on the topic. Like Associate Professor Osborne, he has published widely in the field. He has had a continuing involvement in mammography and other breast investigations since 1975. 87 There is no doubt, as Hoeben J pointed out, that each of the two doctors "is an experienced and highly qualified radiologist with a particular interest in breast imaging". 88 In these circumstances, his Honour was entirely justified in taking the view that the resolution of the conflict of opinion between Associate Professor Osborne and Dr Kitchener could not be achieved "by reference to any superior expertise on the part of either of them". 89 It was a matter for his Honour, as the trial judge, to determine the differences in opinion between the two experts. In carrying out this exercise, it was a matter for him to determine what weight should be attributed to their expertise, qualifications and experience - as it was in regard to the other relevant factors. His Honour made no error in principle in deciding that the issue could not be determined by weighing up the expertise of these two specialists who were both eminent in their field. Once the experts were properly qualified, it is perfectly understandable that his Honour would wish to determine the differences between them by reference to the logical force of their testimony, the evidence as a whole, and questions of demeanour. 90 In my view there is no substance in the argument that Hoeben J should have preferred the opinion of Associate Professor Osborne because his qualifications, in some way, were greater than those of Dr Kitchener.

Professor Levi and Dr Varnava 91 Hoeben J considered that evidence given by Professor Levi, an oncologist who testified on behalf of Mrs O'Gorman, provided support for the conclusion of Dr Kitchener that the mass on the 2006 films was significantly larger than that on the 2004 films. 92 In a report dated 27 November 2007, Professor Levi made two relevant points about the 2006 mammogram. Firstly, he stated: "[The 2006 mammogram] clearly shows an irregular, fairly well circumscribed density within the upper part of the breast centrally. The measurements taken by myself of this mass are 3 x 3.5 cm (sic)."

Secondly, he agreed with Dr Kitchener that the mass shown in the 2006 mammogram was "obvious". 93 According to Dr Kitchener, the dimensions of the mass he observed in the 2006 mammogram were 35 x 30 x 28 millimetres. There is no evidence that Associate Professor Osborne measured the mass. He merely maintained the view that the size of the mass in 2006 was approximately the same as it was in 2004 (while acknowledging that it was denser), subject to the minor qualification that he had "no problems that it could be marginally bigger". Nevertheless, according to Hoeben J, Associate Professor Osborne disagreed with Dr Kitchener's measurements. 94 To the extent that Professor Levi measured the mass, his measurements, as Hoeben J pointed out (at [95]), coincided with two of those recorded by Dr Kitchener. In context, therefore, I am unable to detect any error on the part of Hoeben J in finding that Professor Levi's evidence lends support to the opinion of Dr Kitchener. 95 Hoeben J also considered that the evidence of Dr Varnava supported the conclusion of Dr Kitchener and the appellant contends that his Honour erred in this respect. 96 Dr Varnava said in regard to the 2006 mammogram, "the previously reported 2.5 cm mass … has increased in size to 3 cm". Hoeben J (at [93]) pointed out that, even if the other dimensions had remained unchanged, this represented an increase in size of approximately 20%. 97 Of course, an increase in size of approximately 20% in regard to one dimension does not establish an approximately doubling in size. Nevertheless, Dr Varnava's opinion that the one dimension had increased by approximately 20% is inconsistent with the views expressed by Associate Professor Osborne. To this extent, Hoeben J was correct in saying that Dr Varnava provides "some support" for the conclusion of Dr Kitchener. 98 In the circumstances I would not uphold the appellant's arguments based on Hoeben J's reliance on the testimony of Professor Levi and Dr Varnava.

Did Hoeben J impermissibly take into account his own opinion in interpreting the expert evidence 99 The appellant contends that his Honour erred "in taking into account his own opinions regarding the interpretation of the mammograms formed by his observations of the mammograms". 100 The appellant's argument on this issue was set out in its written submissions as follows: "The 'reading' of the mammogram involved interpretation of that which was observable. That interpretation required application of expertise. It was not as simple as, for example, looking at a colour photograph or placing a ruler on a graph and measuring distance between peaks or simply observing where a mark appeared on a chart. It is quite unlike a process of observing what appears on a photograph; what appear as shadow-like structures of varying density need themselves to be interpreted. What appears to an untrained eye, such as his Honour's, may be quite different to that which a trained observer sees. His Honour, having indicated that, to his observation, the mass under consideration had markedly increased in size upon comparing the two mammograms, he should have pointed out to the experts (particularly to Associate Professor Osborne, with whom he disagreed) what were the features which [led] him to the conclusion that he was tending towards and invited Associate Professor Osborne's response. He did not do so. The appellant could hardly know what was in his Honour's mind and, in any event, should not be in a position to have to enquire. The appellant was irretrievably disadvantaged by his Honour's conclusion." 101 At trial, during the presentation of the evidence of Associate Professor Osborne and Dr Kitchener, the 2006 and 2004 mammograms were displayed in court. As the trial judge recounted (at [90]), the general position of Associate Professor Osborne was that, owing to the difficulties of mammography, it was difficult to make accurate measurements of the mass based upon it. Dr Kitchener's view, on the other hand, was that the change in size (as revealed by a comparison of the two films) was so obvious that there was no need to engage in any precise measurements, even though he had done so. 102 The trial transcript recorded the following exchange between the two experts while observing the displays of the mammograms (at Black 124-125): "WITNESS KITCHENER: This is certainly a true craniocaudal view. So this is a partial view of the same. These two, number 1 and number 2, are craniocaudal and number 3 and number 4 are mediolateral. If you just compare the size of the mass there to the size of the mass there, I don't think it requires a measurement to tell the difference. WITNESS OSBORNE: On the contrary. I think if you take that measurement there to that measurement there which is going through 1, 2, 3, 4 and that measurement there to there, it's still going through 1, 2, 3, 4. What I suggested was that they were approximately the same size. I have got no problems that it could be marginally bigger but what I am saying is that this actually appears denser, easier to see, and therefore as it is easier to see one can see the margins more clearly. But if you actually go from there to there and there to there, it is still approximately the same size, but it is denser. HIS HONOUR: I will just continue with Dr Kitchener. You have heard what Professor Osborne says. Do you agree with that? WITNESS KITCHENER: Not at all. If you look at this image there you can see the margins of the mass perfectly clearly. You can see the back of it and the front of it. If there is some discussion of where the top end of it and the bottom is, you can certainly see the front and back and you can certainly see the front and back there." 103 His Honour found (at [99]) that the mass had in fact doubled in size since the 2004 mammogram. In arriving at that conclusion, his Honour said (at [92]): "As a lay person I found that the comparisons of the size of the mass in the films on which Dr Kitchener relied clearly demonstrated to the naked eye that the 2006 mass was significantly larger. In that regard I appreciate my limitations in that I am not experienced in interpreting mammographic films. I cannot, however, ignore my observation that on a simple visual comparison the mass on the 2006 films appeared significantly larger than that on the 2004 films."

And (at [96]): "In determining this issue, I have also taken into account my assessment of the respective witnesses. Both doctors strongly supported their respective points of view. I found Dr Kitchener, however, ready to make concessions where appropriate, and to approach the questions with a rather more open mind than Associate Professor Osborne. In the case of Associate Professor Osborne I felt that he was very protective of the BreastScreen procedures and that this did inevitably colour his responses. Generally speaking, although both witnesses sought to assist the Court, I found Dr Kitchener's approach to be more considered and reasonable."

Then finally (at [98]-[99]): "I cannot accept the opinion of Associate Professor Osborne that the size of the mass in 2006 was approximately the same as in 2004. There is no support for this opinion other than Associate Professor Osborne's own assertion. Leaving aside the assessments of Dr Kitchener and Professor Levi, and my own observation of the mammogram films, this opinion is clearly in conflict with that of Dr Varnava. Dr Varnava's measurement of one of the dimensions showed an increase of at least 20%. In my opinion, a difference of 20% cannot be correctly characterised as 'approximately the same size'. On this issue I am satisfied that the opinion of Associate Professor Osborne is incorrect and I prefer the evidence of Dr Kitchener. Doctor Kitchener's evidence is substantially supported by that of Professor Levi and as to one measurement at least, by Dr Varnava. It also accords with my own observation of the mammographic scans. Once the opinion of Associate Professor Osborne is rejected, the only guidance which I have is the assessment of Dr Kitchener that the 2006 mammogram showed that the posterior mass had approximately doubled in size since the 2004 mammogram. That is the finding which I make." 104 The appellant contends that his Honour fell into error when he observed that he could not ignore his observation (at [92]) that "on a simple visual comparison" the mass had increased in size between 2004 and 2006 and (at [99]) that the evidence of Dr Kitchener accorded with is own observation of the mammograms. According to the appellant, his Honour thereby impermissibly took into account his own personal interpretation of the mammograms, as he was not qualified to do. The appellant argued that his Honour "should have pointed out to the experts (particularly to Associate Professor Osborne, with whom he disagreed) what were the features which led him to the conclusion that he was tending towards and invited Associate Professor Osborne's response". 105 The principles informing judicial fact-finding and the receipt and interpretation of expert evidence were recently considered by this Court in Strinic v Singh [2009] NSWCA 15. In that case, the trial judge (a District Court judge and former Compensation Court judge of many years standing) made several findings and inferences of fact as to the appellant's medical condition. These were not supported by medical evidence but were the product of the trial judge's own medical knowledge. In allowing the appeal, Beazley JA set out the relevant principles (at [60]-[65]): "The fundamental judicial obligation to make findings of fact on proved evidence (not being matters of common knowledge or judicial knowledge) has been emphasised by the courts in a variety of different circumstances. In Saunders v Adderley [1999] 1 WLR 884, Sir John Balcombe, in delivering the judgment of the majority of the Privy Council, stated, at 889: 'It is, of course, an error of law for a judge to make a finding of fact which there is no evidence to support, unless the matter is one of which the judge is entitled to take judicial notice.' … Even if a particular judge sitting in a court of general jurisdiction is experienced in adjudicating medical cases, that experience does not replace the requirement to base findings on the evidence. A court cannot assume that its knowledge of any particular matter is correct, even if the individual judge has a great deal of experience dealing with, for example, medical issues, as was the case here. In Saunders v Adderley [1999] 1 WLR 884 it was said that such a process involved an error of law. Underlying that error is a fundamental breach of procedural fairness. A party is not afforded procedural fairness where a trial judge makes findings of fact based upon that judge's own purported knowledge or understanding of matters that do not form part of the evidence. I have put that proposition in blunt terms, because it is the underlying fundamental principle upon which courts must act. Procedural fairness does, however, take its colour and hue from the particular circumstances at hand. Thus, a specialist tribunal will have greater leeway in applying its specialist knowledge, either because the constituting statute so provides, or because the parties are taken to understand its practices. Such tribunals are often the sole and final determiners of fact. Likewise, a trial judge would be entitled to advise the parties that he understood certain medical evidence to have a particular meaning, even if that meaning was not stated in the evidence. If all parties agreed that the judge's understanding on that matter was correct, then, the matter being transparent and not in dispute, there would be no breach of procedural fairness in the trial judge's acting on that understanding." 106 This is not a case where the above principles were offended. 107 During the course of the testimony of the two experts, his Honour said to senior counsel then representing the appellant: "[T]here is an issue about the size of the mass. I simply want him to point out and say there's the mass … ." 108 His Honour then asked Dr Kitchener if the films being viewed showed the mass. Dr Kitchener replied that they did and indicated where in the films the mass was to be seen. Associate Professor Osborne then, while pointing to parts of the film that was being displayed, said, "if you go from there to there and there to there, it is still approximately the same size … ." 109 Hoeben J thereupon asked Dr Kitchener whether he agreed with Associate Professor Osborne. Dr Kitchener replied, "not at all". He said: "If you look at this image there you can see the margins of the mass perfectly clearly. You can see the back of it and the front of it … ." 110 His Honour pointed out a difficulty he had with certain images and Dr Kitchener replied by referring to "an anterior margin down here and a posterior margin down here". 111 Associate Professor Osborne thereupon pointed to parts of the film and said "if you actually look here you can see the inferior margin but you can't actually see the superior margin well". He said, "If you take that measurement to that measurement and that measurement to that measurement, once again just measuring on the scales that have been drawn here, they are approximately the same." Dr Kitchener responded by reference to aspects of the film being viewed. His Honour specifically asked Dr Kitchener to identify a particular feature of the film to which he had referred and Dr Kitchener did so as well as identifying other features. 112 The testimony proceeded in this fashion. Both witnesses identified parts of the film they considered supported them and the judge asked questions to clarify matters for himself. 113 The procedure so adopted was entirely orthodox. The experts explained by reference to the films being displayed in court the features they considered important and the attention of the judge was drawn to those matters each considered relevant. His Honour then decided by reference to what he had seen and heard which opinion he preferred. This is how our system of adversarial justice works. There is nothing in this exercise that suggests that his Honour sought to apply his own knowledge to what he had been told by the witnesses. 114 None of his Honour's reasoning on this issue could have come as a surprise to the appellant. That reasoning reflects the testimony given, his Honour's questioning of the witnesses and their replies. The approach taken by his Honour did not occasion a breach of procedural fairness. The appellant had every opportunity to put its case to his Honour on this issue and did so through the evidence of Associate Professor Osborne and the questions and submissions of its counsel. 115 Hoeben J expressly disavowed any relevant expert knowledge on his part and acknowledged (at [92]) his limitations in this regard. Nothing in his Honour's reasons indicates that he acted contrary to this approach. His Honour did not base his assessment of the change in size of the mass upon his own medical knowledge or experience of interpreting mammograms. I would reject this ground of appeal.

Causation 116 The facts relevant to causation fall within a small compass. They are as follows:

(a) The appellant's radiologists failed to detect from the mammogram taken on 23 February 2006 that there were suspicious signs of malignancy in Mrs O'Gorman's left breast.

(b) On the findings of Hoeben J that failure was negligent.

(c) Had the malignancy been detected and treated immediately after the mammogram of 23 February 2006, there was a 38 per cent chance of a metastatic tumour, in any event, developing elsewhere in Mrs O'Gorman's body. I understand this to mean that 38 persons out of 100 in Mrs O'Gorman's position would have experienced the tumour metastasising (even had treatment immediately occurred), and 62 persons out of 100 in that position would not.

(d) On 17 January 2007, when further examination resulted in the detection of the tumour, there was a 42 per cent chance of metastasis occurring elsewhere in Mrs O'Gorman's body.

(e) In fact metastasis occurred, and tumours spread. 117 A further fact is highly significant to the causation issue. This concerns the extent of the increase of the risk of metastasis caused by the failure of the appellant to detect the tumour in March 2006. There is an issue between the parties as to whether this risk was found by his Honour to relate to Mrs O'Gorman personally (that is, to her as an individual) or whether it was merely another piece of general epidemiological evidence. Hoeben J said in this regard (at [137]): "There was no material difference between the evidence of Professors Levi and Tattersall as to the survival rates attached to a diagnosis of breast cancer in March 2006, rather than January 2007, and the percentage likelihood of metastasisation. The effect of their combined opinion is that the risk of the plaintiff's breast cancer metastasising between March 2006 and January 2007 increased by approximately 10%. That figure was agreed by the parties in their written submissions." 118 His Honour's statement in [137] concerning the effect of the "combined opinion" of the two experts constitutes a finding of fact that, as articulated, concerns the risk to the plaintiff individually, not to her as a part of a statistical segment of the population. 119 The appellant did not appeal against that finding and, in argument on appeal, Mr Menzies QC (who together with Mr Hodgson appeared for the appellant) challenged it only in reply. Presumably Mr Menzies thought that a reply was called for as Mr B Toomey QC (who together with Mr D Toomey appeared for the respondent) relied on the finding, submitting (correctly) that the finding was not epidemiological evidence. Mr Menzies submitted that, notwithstanding his Honour's formulation of the experts' combined opinion, the increase in risk to the plaintiff of about 10 per cent was indeed epidemiological evidence as it involved merely a mathematical extrapolation from two pieces of epidemiological evidence that were common ground. The first was that, in March 2006, the tumour would have metastasised (even had treatment immediately occurred) in 38 persons out of 100 in Mrs O'Gorman's position, but this would not have occurred in 62 persons out of 100 in that position. The second was that, by January 2007 (even had treatment then occurred), the risk had increased to the extent that the tumour in 42 persons out of 100 in Mrs O'Gorman's position would have metastasised (and metastasis would not have so occurred in 58 persons). 120 According to Mrs O'Gorman's written closing submissions at trial, "between the beginning of 2006 and her diagnosis with breast cancer in 2007, the plaintiff's risk of developing metastasis increased by more than 10%". This was a submission that the risk to the plaintiff, personally, had increased by more than 10 per cent. The appellant's written closing submissions at trial did not deal with the issue. Mr Menzies, in oral closing submissions at trial, said (Black 196), "metastasisation was likely in the percentages that the medical practitioners have said. If the defendant was negligent it affected arguably the outcome." Mr Menzies, quite properly, accepted before this Court that he had indicated to Hoeben J that the risk to the plaintiff, herself, increased (appeal transcript 38.41). 121 The issue whether the appellant may now disavow any acceptance that the risk to the plaintiff increased by about 10 per cent is a difficult one, but in the light of the matters to which I have referred in this connection, I incline to the view that it cannot now resile from that acceptance. I shall deal with the matter on that basis and also on the basis that my view on this issue may be wrong. 122 Mr Toomey submitted that the governing principal was that "a material increase in risk equates to a material contribution provided the risk eventuates". 123 In my reasons in Flounders v Millar [2007] NSWCA 238 (with which Handley AJA and Hoeben J agreed) I discussed this proposition and cases relevant to it. I do not propose to repeat everything that I said there. I would however make the following comments. 124 The notion that there is an equivalence between a material increase in the risk of injury and a material contribution to injury has been refuted in this Court by Bendix Mintex Pty Ltd v Barnes (1997) 42 NSWLR 307 especially at 315 - 316 and TC by his tutor Sabatino v The State of New South Wales [2001] NSWCA 380 where Mason P explained (at [59]): "A defendant who exposes a plaintiff to a risk of injury or who, by omission, fails to take reasonable steps to avoid or minimise that risk is not liable unless the risk comes home in the sense that the court is ultimately satisfied on the balance of probability that the defendant's breach caused or materially contributed to the harm actually suffered."

See also Roads & Traffic Authority v Royal [2008] HCA 19; (2008) 82 ALJR 870. 125 In Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; (2000) 49 NSWLR 262; Spigelman CJ (with whom Davies AJA agreed; Stein JA dissenting) said (at [119]): "There is a tension between the suggestion that any increased risk is sufficient to constitute a 'material contribution', and the clear line of authority that a mere possibility is not sufficient to establish causation for legal purposes. The latter is too well established to be qualified by the former. The reconciliation between the two kinds of references is to be found in the fact that, as in Chappel v Hart [1998] HCA 55; (1998) 195 CLR 232; and in the cases that suggest the former, the actual risk had materialised. The 'possibility' or 'risk' that X might cause Y had in fact eventuated, not in the sense that X happened and Y had also happened, but that it was undisputed that Y had happened because of X." 126 Workers' Compensation (Dust Diseases) Board v Veksans (1993) 32 NSWLR 221 illustrates the fallacy in the proposition that a mere material increase in the risk of injury followed by the eventuation of the risk in question is sufficient to establish causation. In that case there was evidence that exposure of non-smokers to asbestos increases the risk of lung cancer five times, that smoking increases the risk ten times but that smoking and exposure to asbestos increases it more than 50 times. Nevertheless, persons who have not been exposed to asbestos contracted lung cancer, and the lung cancer rate among smokers exposed to asbestos was still only 601 per 100,000. Handley JA (with whom Sheller JA agreed) pointed out (at 241) that although smokers exposed to asbestos at work had a greatly increased risk of contracting lung cancer, this "did not necessarily establish that this worker's lung cancer was in fact caused or contributed to by his exposure to asbestos". 127 In Gett v Tabet [2009] NSWCA 76 Allsop P, Beazley JA and Basten JA agreed (at [254]) - as held in Flounders v Millar - that a "material increase in risk was not to be equated with material contribution to the injury and that the plaintiff must establish that it was probable that the risk created by the tortfeasor came home". Their Honours stated (at [256]): "There is no mechanical legal rule of causation based on the creation of risk, whether founded on a shifting evidential onus or otherwise, as submitted by the respondent. The passage in Betts v Whittingslowe [1945] HCA 31; (1945) 71 CLR 637 at 649 reflects the entitlement of the fact finder to gain assistance from the existence of the breach of duty, the kind of risk produced by that and the damage that occurred in drawing relevant inferences from these matters as to causation: See Roads & Traffic Authority v Royal [2008] HCA 19; (2008) 82 ALJR 870 (at [31] and [143])". 128 Mr Menzies submitted that the present case was on all fours with Gett v Tabet. As the court held in Gett v Tabet that causation had not been proved, Mr Menzies submitted that, applying the same reasoning, Mrs O'Gorman had failed to prove causation in the present case. 129 In Gett v Tabet the respondent was diagnosed with a brain tumour on 14 January 1991. The diagnosis was made following a seizure, CT scan and EEG and was preceded by a history of chickenpox, as well as headaches, nausea and vomiting. The respondent received treatment, including surgery to remove the tumour. Following the treatment, she suffered irreversible brain damage caused partly from the tumour (which had been growing for over two years), and partly from the operative procedure and other treatment (not said to be in any way negligently performed). The respondent brought proceedings against the appellant, a specialist paediatrician, alleging that he had been negligent in his treatment of her. The primary allegation was that the CT scan should have been done earlier, either on 11 January or 13 January, and that if it had, she would have had a better medical outcome. 130 The trial judge found that the appellant breached his duty of care by failing to order a CT scan on 13 January 1991. His Honour held that, had a CT scan been performed on that date, the brain tumour would have been detected. His Honour concluded that the respondent lost a chance of a better medical outcome because of the appellant's negligence. 131 One of the grounds of appeal was that the trial judge failed to hold that the negligence was not causative of loss. This ground was upheld on appeal. This Court found (at [243]) that, at the most, on the evidence, the respondent lost some chance of a better outcome which ranged between "speculative and some effect". Their Honours noted (at [244]) that the evidence in question "illuminated the legitimacy" of the trial judge's conclusions as to the lack of evidence on the balance of probabilities that the damage suffered on 14 January by the seizure and deterioration would have been avoided had the appellant acted with due care and ordered a CT scan on 13 January. In essence, their Honours found that the respondent had failed to prove on a balance of probabilities that, had the appellant ordered a CT scan on 13 January 1991, there would have been a better medical outcome. 132 Critical to the outcome in Gett v Tibet was the respondent's inability to prove on a balance of probabilities that her injuries would have been avoided, or she would have been better off, had the CT scan been performed earlier. The prospects of the respondent improving were, at most, speculative. 133 In comparing the facts of the present case with Gett v Tabet, it is necessary to determine the effect of the evidence that, had the malignancy been detected and treated immediately after the mammogram of 23 February 2006, there was only a 38 per cent chance of a metastatic tumour developing elsewhere in Mrs O'Gorman's body and that the failure, during the period between March 2006 and January 2007, to detect the malignancy in the 2006 mammogram increased the risk of Mrs O'Gorman's breast cancer metastasising by approximately 10 per cent. 134 There are dangers in applying evidence that tends to quantify possibilities mathematically. In Re JS (a minor) [1980] 1 All ER 1061 Ormrod LJ, giving the judgment of the English Court of Appeal (constituted by himself and Orr LJ), said (at [1066]): "The concept of 'probability' in the legal sense is certainly different from the mathematical concept: indeed, it is rare to find a situation in which these two usages co-exist although, when they do, the mathematical probability has to be taken into the assessment of probability in the legal sense and given its appropriate weight." 135 There are also dangers in applying epidemiological or statistical evidence in a mechanical way: Seltsam Pty Ltd v McGuiness. 136 In State Government Insurance Commission v Laube (1984) 37 SASR 31 the question before the court was whether a driver with a blood alcohol reading of 0.155 per cent about an hour after the accident was at the time of the accident incapable of exercising effective control of a vehicle. An expert witness testified that the majority of drivers with that blood alcohol level would not be able to exercise effective control of a motor vehicle, but some would or might be so capable. King CJ (at [32 - 33]) observed: "The most that can be said is that it is statistically more probable than not that any individual with such a blood alcohol level would be incapable of exercising effective control. … I am clearly of the opinion that the statistical fact that a particular proposition is true of the majority of persons cannot of itself amount to legal proof on the balance of probabilities that the proposition is true of any given individual."

State Government Insurance Commission v Laube has been followed in Payne v Crawford (1992) 3 Tas R 360 (per Zeeman J) and R v Mitchell (1997) 130 ACTR 48 (per Higgins J). 137 In my respectful opinion, it is overstating the position to say that, as an absolute proposition, "the statistical fact that a particular proposition is true of the majority of persons cannot of itself amount to legal proof on the balance of probabilities that the proposition is true of any given individual". In my opinion, the matter is essentially one of degree. This is demonstrated by Spigelman CJ's discussion of epidemiological evidence in Seltsam Pty Ltd v McGuiness. In that case the Chief Justice considered in depth the use that may be made of epidemiological evidence in establishing causation. 138 Seltsam Pty Ltd v McGuiness (at [89], [98], and [153]) EMI Australia Ltd v BES [1970] 2 NSWR 238 at 242 (appeal dismissed (1970) 44 ALJR 360); and Fernandez v Tubemakers of Australia Ltd [1975] 2 NSWLR 190 at 239, 240 are authority for the proposition that evidence of epidemiological studies is circumstantial evidence which may, alone, or in combination with other evidence, establish causation in a specific case. The fact that experts do not infer causation on a balance of probabilities does not mean that a court may not: Seltsam Pty Ltd v McGuiness at [143]-[144]. A finding of causal connection may be made even when the expert evidence does not rise above the possible; the question is always whether the evidence as a whole establishes causation on a balance of probabilities: Seltsam Pty Ltd v McGuiness at [89], [94]-[96], [98]-[100], [102], [143], [144] and [153]. 139 What is meant by "balance of probabilities" in this context? Guidance may be obtained from the remarks of Mahoney JA in Jones v Sutherland Shire Council [1979] 2 NSWLR 206 where his Honour, in commenting on this issue, said (at [227]): "The first step, in a sense, involves simply an assessment of what is human experience: it is, or is not, a fact that human experience is so. But such an assessment is not made as a mathematical calculation. It involves other kinds of reasoning in judgments, the correctness of which cannot be demonstrated by mathematics or ordinary logic. Therefore, the subjective confidence which a person or a court will have in the correctness of the assessment may vary. It is to this that, in my opinion, phrases such as 'the balance of probabilities' refer in respect of such an assessment." 140 Mahoney JA observed that one possible meaning of a thing being "probable" is where the person, judging the probability of that thing, "has the appropriate degree of confidence in its existence or correctness based on or judged according to reason". His Honour remarked (at [227-228]): "It is in this sense that 'probability' is used in determining whether a particular proposition of fact should be accepted for the purpose of litigation. It was in my opinion to this that Dixon J referred in Briginshaw v Briginshaw [1938] HCA 34; (1938) 60 CLR 336 at 361. In referring to what constituted proof of a fact, his Honour said: ' … the tribunal must feel an actual persuasion of its occurrence or existence before it can be found. It cannot be found as a result of a mere mechanical comparison of probabilities independently of any belief in its reality'." 141 These observations echo his Honour's remarks in Fernandez v Tubemakers of Australia Ltd at 199 (quoted by Spigelman CJ in Seltsam Pty Ltd v McGuinness at [95] and [99]) and with respect, are not inconsistent with what is said in Flounders v Millar at [35], namely: "It remains necessary for a plaintiff, relying on circumstantial evidence, to prove that the circumstances raise the more probable inference in favour of what is alleged. The circumstances must do more than give rise to conflicting inferences of an equal degree of probability or plausibility. The choice between conflicting inferences must be more than a matter of conjecture. If the court is left to speculate about possibilities as to the cause of the injury, the plaintiff must fail. … The rules governing causation at common law are those expressed in Luxton v Vines and March v Stramare (E & M H) Pty Limited , namely, the test of commonsense, with the onus of proof at all times being on the plaintiff". 142 Mr Menzies submitted, in effect, that the fact that, epidemiologically, 62 per cent of persons who had breast cancer such as Mrs O'Gorman had in March 2006 would not have experienced any metastatic effect had that cancer been detected and treated at that time, does not prove that Mrs O'Gorman was not part of the 38 per cent who would have experienced metastasis, in any event. 143 It is not necessary to decide whether this submission is correct as there is other, additional evidence on which the appellant relies to establish causation, namely, the increase in the risk of metastasis by 10 per cent that occurred between March 2006 and January 2007. 144 Statistically speaking, Mrs O'Gorman had a 62 per cent chance of not experiencing metastasis. That being so, I would comment (without deciding the issue) that it is reasonably arguable - on a common sense basis - that if 62 persons out of 100 in Mrs O'Gorman's position would not have experienced metastasis had the cancer been detected and treated in 2006, it is probable that Mrs O'Gorman's cancer would not have metastasised had it been detected and treated in March 2006. 145 I would add that, while this statistic does not necessarily establish proof on a balance of probabilities (although it arguably does), in my opinion - at the very least - it shows that there was a strong possibility that, had the tumour been detected in March 2006, Mrs O'Gorman's cancer would not have metastasised. On this ground alone, this case is materially different from Gett v Tabet. 146 The evidence that the failure to diagnose increased the risk of metastasis by 10 per cent between February 2006 and January 2007 is another strand in the causation cable. For the reasons I have previously given, I shall first deal with the effect of that evidence on the basis that it is not epidemiological evidence but evidence that the risk to Mrs O'Gorman, as an individual, increased by 10 per cent. That is on the basis that it is not now open to the appellant to resile from its acceptance that there was an increase in the risk to Mrs O'Gorman personally and not as a member of a segment of the population. 147 Evidence of the increase by 10 per cent of the risk to Mrs O'Gorman as an individual is of particular significance as it is not epidemiological evidence but is evidence that applies, singularly, to Mrs O'Gorman. This evidence further differentiates this case from Gett v Tabet. Whether this evidence does in fact prove causation is a matter of evaluative judgment based on the criteria referred to in Luxton v Vines (1952) 85 CLR 352, March v Stramare (E & M H) Pty Limited [1991] HCA 12; (1991) 171 CLR 506, Fernandez v Tubemakers of Australia Ltd, Seltsam Pty Ltd v McGuiness, EMI (Australia) Ltd v BES, and Jones v Sutherland Shire Council. 148 As I have stated, there was, at least, a strong possibility that, had the radiologists detected the tumour, it would not have metastasised. Not a great deal of evidence would be required to tip the scales from that strong possibility to a finding that, on a balance of probabilities, the failure to detect the tumour led to the metastasis. 149 The increased risk to Mrs O'Gorman as an individual made it more likely that the tumour would metastasise and the risk was increased to an extent that was not negligible. In my opinion, that evidence is significant and is sufficient to tip the scales. By the failure to detect and treat Mrs O'Gorman's cancer, the risk of metastasis increased by about 10 per cent, not statistically but personally to her. She was directly rendered more susceptible to metastasis. In my opinion, applying the common sense test of causation, I am satisfied that the failure in March 2006 to detect and treat the cancer caused the metastasis. 150 I now turn to the same issue but on the basis that the evidence as to an increase in the risk was not evidence that applied to Mrs O'Gorman personally, but was epidemiological evidence. 151 The starting point, again, is the fact that epidemiological evidence is only evidence of possibility. I repeat, however, that epidemiological evidence may alone establish causation in a specific case. 152 Assume that epidemiological evidence shows that is a 99 per cent chance that no metastasis will result from a detected and treated tumour (and the prospect that metastasis would occur in any event is one per cent). In my view, that evidence alone would establish causation where there was a failure to detect a tumour and metastasis followed. 153 The statistical position in the present case is that in March 2006 the prospect of metastasis not occurring (had the tumour been detected and treated) was 62 per cent. I have found that that evidence establishes, at the least, a strong possibility that, had the tumour been detected in March 2006, no metastasis would have occurred. The question is whether the increased epidemiological risk of Mrs O'Gorman experiencing metastasis because of the failure to detect the tumour is sufficient to convert the strong possibility into a probability. 154 In my view, that question must be answered in the affirmative. This is essentially an evaluative decision based on common sense. I can express the reasoning behind my conclusion no better than by paraphrasing Mahoney JA's remarks in Fernandez v Tubemakers of Australia Ltd (at 200). I consider that the evidence showed that the connection between the appellant's negligence and the subsequent tumours that metastasised was sufficiently close to warrant a reasonable mind concluding on a balance of probabilities that the appellant's negligence was the actual cause of the tumours that metastasised. 155 I would therefore dismiss the appeal against the decision as to causation.

The rejection of parts of the evidence of Drs Van Rooijen and Varnava 156 The appellant tendered the disallowed evidence on the basis that it was expert evidence or alternatively, direct evidence of fact. Hoeben J rejected the evidence on both bases. 157 During the course of argument on appeal it became clear that the questions raised by the admissibility issues were the following:

(a) Was the evidence in question expert evidence or evidence as to facts, not in the nature of expert evidence?

(b) If the evidence was expert evidence, was its admissibility subject to the rules of court relating to expert evidence (contained in Pt 31 of the Uniform Civil Procedure Rules 2005 - "the UCPR")?

(c) If the rules of court relating to expert evidence were applicable to the disallowed evidence, what effect did the rules have upon the admissibility of that evidence?

(d) If the disallowed evidence was expert evidence, was it admissible despite the fact that it was to be given by the two radiologists who were alleged to have negligently caused the metastasising tumours?

(e) How do the relevant provisions of the Evidence Act 1995 affect the admissibility of the disallowed evidence?

(f) Taking into account the answers to all of the above questions, did his Honour err in refusing to allow the evidence?

(g) If the evidence was wrongly disallowed, should a new trial be ordered?

The evidence that was disallowed and his Honour's reasons for disallowing it 158 Because of the parlous state of Mrs O'Gorman's health, the proceedings below were expedited. Mrs O'Gorman's statement of claim was filed on 19 June 2008 and the trial commenced less than four months later. Hoeben J recorded that both sides, in particular the appellant, "co-operated significantly so as to enable the matter to come on for hearing and be completed expeditiously". For this reason, the UCPR rules relating to exchange of witness statements and experts' reports were not rigorously complied with and his Honour, quite properly, allowed the parties, particularly the appellant, a degree of latitude in complying with the time periods laid down by the UCPR. I mention this aspect of the matter as it does cast some light on the way in which the appellant dealt with the disputed evidence of Drs Van Rooijen and Varnava. 159 The evidence in chief of Drs Van Rooijen and Varnava was set out in written statements that were exchanged. Before their evidence was tendered, however, the appellant tendered the testimony of Dr David Stephen, a radiologist employed by BreastScreen, who reviewed Mrs O'Gorman's 2004 mammograms and also her mammograms taken in 1998 and 2002. It is necessary to refer in some detail to parts of Dr Stephen's evidence and how Hoeben J dealt with them as, when rejecting parts of the statements of Drs Van Rooijen and Varnava, his Honour referred (impliedly in the case of Dr Varnava) to the rulings he made concerning Dr Stephen's evidence. 160 On the second day of the hearing, 9 October, the appellant sought to tender evidence in the form of a statement by Dr Stephen. That statement included the following paragraphs: "18 The 2004 films do not show any evidence of malignancy. The films do not show any pathology that warrants a recall. 19 There are cysts present in the breast tissue, however it is normal for women to have cysts in the breast tissue. Cysts are hormonal and the appearance of cysts often varies between films and the cysts often disappear. Previous examinations showed cystic disease and these would have been reviewed.

20 I have reviewed the 1998 and 2002 films. I may have had access to the 1998 and/or 2002 films when I initially reported on the 2004 films. There is no evidence of malignancy in any of the earlier films and that and the presence of cysts in the 1998 and the 2002 films reassures me that recall was not warranted in 2004. 21 The 'abnormality' evident in the 2004 films by which Dr Kitchener refers to is a cystic mass. A cystic mass is not evidence of malignancy, it is quite expected and common in many women in their 50s and the system does not allow for radiologists to provide a detailed description of the appearance of the films, but rather to indicate (if the films are technically adequate) whether or not the films were normal (and cysts are normal) or required the patient to be recalled. It is only in the latter case that a form is completed which describes the abnormality/suspicious circumstances and makes a recommendation regarding the further assessment required." 161 Mr Bartley SC, who appeared for the respondent at trial, objected to paragraphs 18 to 21. The only ground of objection that Mr Bartley articulated was that Dr Stephen was "expressing an opinion which is by way of ex post facto" (Black 58). 162 Hoeben J upheld the objection with respect to paragraphs 20 and 21, stating: "[H]ow do you get in [these paragraphs], which [are] pure opinion? It has nothing to do with his state of mind in 2004. It is argumentative and it is in the nature of an expert opinion. …

I will allow 18 and 19 but I am not going to allow somebody who is directly involved and who is here for factual purposes, to come in and express this kind of expertise or this kind of expert opinion." 163 Mr Menzies then invited his Honour to consider the paragraphs as expert opinion. Hoeben J, however, rejected this attempt as well, stating: "That is why I allow 18 and 19. Because it would be ludicrous to suggest that the doctor has any independent recollection now of what he thought in 2004. But with his knowledge and expertise it seems reasonable to allow him to extrapolate and say, looking at the films now, this is what I see. By inference, this is what I saw in 2004. But the other is in the nature of an expert report. It should have been dealt with as an expert report and it hasn't been." 164 There is, with respect, some inconsistency in his Honour's ruling in relation to paragraphs 18 - 21 of Dr Stephen's statement. Paragraphs 20 and 21 undoubtedly contain expert evidence. But, so do paragraphs 18 and 19. As I shall later indicate, his Honour subsequently appeared to recognise this but did not alter his decision in relation to paragraphs 18 and 19. 165 I draw attention to his Honour's comment that Dr Stephen's report "should have been dealt with as an expert report and it hasn't been" (this was not an objection that Mr Bartley had raised). Mr Toomey sought to obtain some assistance from this remark and submitted that his Honour, in effect, incorporated this observation when later rejecting the disallowed testimony of Drs Van Rooijen and Varnava. 166 On the third day of the hearing, 10 October 2008, the appellant sought to tender evidence in the form of a statement by Dr Van Rooijen. That statement included the following paragraphs: "24 I have recently had an opportunity to view copies of Ms Gorman's 2006 mammogram. There is an obvious mass in the central part of Ms O'Gorman's left breast. The mass is a circumscribed round opacity with well defined margins and a portion of a 'halo' on one of the views. These are typically benign features and a halo is classically associated with a cyst. The small calcification projected over the mass on the mediolateral projection is shown to be outside the mass on the cranio-caudal projection and not relevant to the mass. 25 Given what I believe to be the presence of an obvious mass on the 2006 mammogram, I am certain that the 2002 mammogram would have been placed on the viewer in accordance with standard practice. I say this because if there were no previous mammogram for comparison I would routinely recall for assessment if the mammogram show an obvious mass, even if I thought it had a benign feature, as is the case here with the 2006 mammogram . I would have compared the 2006 mammogram with the 2002 mammogram and I would also have pulled out Ms O'Gorman's file to compare the 2006 mammogram with other previous rounds, and to see whether there had been any previous assessments or comments in the notes (prior to 2000, the reporting was manual not computerised and 'normal' reads frequently had written comments), so as to get a better idea about the nature of the mass present on the 2006 mammogram. This was my normal practice at the time (and it remains my practice) and I have no reason to believe that I did not follow my normal practice in this case. … 27 I believe after viewing the 2002 and 2006 mammograms, I would have looked at Ms O'Gorman's file, reviewed the films from previous rounds and noted the previous history of cysts in her breasts. The lesion centrally located in the left breast on the 2006 mammogram is round with well defined margins and part halo, benign mammographic features consistent with a cyst, and was present over a four year period. These features, together with evidence of other cysts on previous rounds, is the basis upon which I believe that I, correctly, determined that Ms O'Gorman's mammogram was "normal", not requiring recall for assessment." (My underlining.) 167 Mr Bartley objected to the underlined words in paragraph 24 and sought that they be deleted. The only objection Mr Bartley articulated was that the evidence in question was "a reconstruction" (Black 70).

168 Hoeben J upheld the objection to the words in paragraph 24 and also struck out the underlined words in paragraphs 25 and 27. Mr Bartley did not express any objection to the disallowed evidence in the latter two paragraphs but his Honour applied the same reasoning to these paragraphs as he did to the evidence in paragraph 24 that he disallowed. His Honour said in this regard: "In this particular case Dr Van Rooijen has no independent recollection of viewing the mammogram. … I am allowing some ex post facto matters to be adduced because things such as an obvious mass would not have been missed by somebody with her experience, but to allow in particular the material which I have referred to in paragraph 24 would really be to allow ex post facto expert evidence which it is not appropriate for this witness to give. This is because, and I am not being critical in the slightest way, but Dr Van Rooijen simply does not know what her state of mind was at the time, and given the circumstances in which we now find ourselves, litigation, it would simply be unfair and really unreliable to allow her to bring to bear her current observations and understanding of what's happening and say, well, that must have been how my mind worked two years ago. So I am simply not going to allow it." 169 Mr Menzies then submitted that the sentence in paragraph 24 reading, "The mass is a circumscribed round opacity with well defined margins and a portion of a 'halo' on one of the views" was "nothing more than a description of something" and was "not an expression of opinion". Hoeben J rejected this submission. 170 Mr Menzies then submitted that the judge's concerns went "to weight rather than to admissibility". His Honour replied: "I think it goes further than that, Mr Menzies. I am not going to reverse the rulings I made yesterday. I may have been in error, I may have been too generous to your side, but I am not going to reverse them." 171 His Honour, in the last passage, by his reference to having been "too generous" to the appellant, was referring to his decision to admit paragraphs 18 and 19 of the statement of Dr Stephen. During argument on appeal, Mr Menzies suggested that his Honour was thereby saying that the reasons he gave in rejecting evidence from Dr Stephen applied also to his rejection of Dr Van Rooijen. On examining the transcript, however, I do not think that is correct. His Honour referred to his decision in regard to Dr Stephen's testimony only to comment on a possible inconsistency in his treatment of the evidence of Dr Van Rooijen when compared to that of Dr Stephen. His Honour thought that he might have allowed the appellant too much latitude in regard to Dr Stephen's testimony, but did not intend to reverse his decision in that regard. 172 His Honour thereupon formally rejected the words I have underlined in paragraphs 24, 25 and 27 of Dr Van Rooijen's statement.

173 Mr Toomey submitted that Hoeben J, in saying that he was "not going to reverse the rulings" he had made the day before in regard to Mr Stephen, was referring to all the reasons he gave in rejecting Dr Stephen's evidence, including his Honour's statement that Dr Stephen's report should have been dealt with as an expert's report but was not. I do not accept this submission. In my view, it is plain that Hoeben J, by remarking that his concerns went further than the weight to be given to the disallowed evidence, and that they related to the admissibility of that evidence (contrary to Mr Menzies' submission), and that he had been too generous to Mr Menzies' "side" in admitting paragraphs 18 and 19 of Dr Stephen's statement, was saying no more than that the admission of those two paragraphs would not impinge on his approach to Dr Van Rooijen's testimony. In other words, despite admitting paragraphs 18 and 19 of Dr Stephen's evidence (which Hoeben J, apparently, had come to think might be expert evidence) he would maintain his rejection of those parts of Dr Rooijen's evidence that he had already disallowed.

174 At this stage, Mr Menzies had tendered paragraphs 24, 25 and 27 on the basis that they were expert evidence or, alternatively, direct evidence of fact. Hoeben J, in the passages I have quoted, rejected the underlined words on the grounds, only, that they were "ex post facto expert evidence" and that it was not appropriate for Dr Van Rooijen to give that evidence. His Honour, at this point, made no mention of the rules of court. 175 Later on 10 October 2008, the appellant sought to tender evidence in the form of a statement by Dr Varnava. Mr Bartley objected to parts of that statement without articulating his grounds of objection. His Honour rejected most of those parts to which Mr Bartley had objected. For the purposes of these reasons, the rejected parts that are particularly relevant are those set out below: "19 I have reviewed the Plaintiff's 2002 films for the purpose of this statement. …

26 Based on my review of the films in 2008 I maintain my interpretation of the Plaintiff's 2004 mammogram as 'normal' rather than requiring further assessment. …

30 … The 3cm mass has regular smoothly contoured margins although some margins cannot be fully assessed due to the adjacent dense tissue. A halo sign is still present except where the margins are obscured by the adjacent dense tissue. A halo sign is still present except where the margins are obscured by the adjacent parenchyma - a "halo sign" is a thin radiolucent ring along the periphery of the lesion which is a frequent finding in benign lesions and is very rarely indicative of cancer. Some of the films appear magnified and on the CC view, which appears the least magnified, the lesion measures 3cm. No microcalcification lies with this lesion as evidenced by the CC view. … 31 Based on my review of the films in 2008 I maintain my interpretation of the Plaintiff's 2006 mammogram as 'normal' rather than requiring further assessment. This interpretation is based on the following - (a) cysts are very common - the incidence of cysts is reported as occurring anywhere between 20-50% of women in screening and peaks pre-menopause (40-50 years old); (b) the Plaintiff had previous screens showing multiple smoothly contoured lesions; the most common cause for this would be multiple cysts or multiple fibrodenomas and this is seen commonly (multiple times per session) in BreastScreen mammograms; (c) the increase in size of the largest lesion since the previous scan is not dramatic; (d) the increase in size is consistent with benign cystic disease; (e) the halo sign is still present in the largest lesion and although not unique to benign disease, the halo sign is a strong indicator of a benign process; (f) most of the other lesions are no longer present again in keeping with benign cystic disease; (g) the persistence and increase in size of one or two cysts whilst others regress happens commonly in benign disease; and (h) no microcalcification was present in the smoothly contoured lesions to indicated they were solid and not cystic in nature. … 33 In summary the interpretation that the 3cm mass seen in the 2006 mammogram was a cyst was reasonable in view of the Plaintiff's previous mammograms showing multiple lesions consistent with cysts, especially with the presence of a halo sign. The natural history of cysts is that they can increase or decrease in size with some or all resolving and some staying unchanged." 176 In rejecting Dr Varnava's evidence set out in the previous paragraphs, his Honour said, "I believe those rulings are consistent with the earlier debate we have had. If you wish to raise other matters …". Mr Menzies responded, "I have pressed them, your Honour has rejected them. For my part that is where the matter ends". 177 His Honour's reference to the "earlier debate" is ambiguous. It is not clear whether he was referring only to the rejection of Dr Van Rooijen's evidence (which had taken place earlier that day) or whether he also had in mind the reasons he gave for rejecting parts of Dr Stephen's evidence when he dealt with the issue the previous day. 178 During closing submissions, his Honour clarified his reasons for rejecting the evidence. He said: "What I thought was unfair, and regardless of which way I go on the judgment I will spell out exactly everyone's position as to why I rejected that evidence, is I simply found it unreliable to ask people who are being directly attacked or criticised, their conduct, to then become ad hoc experts. Not ad hoc experts but in fact provide expert evidence to, as it were, justify their conduct which is the very conduct under consideration. I just found that unhelpful and that is why I rejected that." 179 Significantly, when spelling out "exactly" why he rejected the all the disallowed evidence, his Honour made no reference to any omission to comply with the relevant rules of court. This suggests that he was distancing himself from this factor. This approach is consistent with the reasons his Honour gave for rejecting the disallowed evidence of Dr Van Rooijen. Thus, his Honour's observations during closing submissions lead to the inference that, when rejecting the disallowed evidence of Dr Varnava, he did not do so by reason of non-compliance with the UCPR. 180 When Hoeben J gave judgment on 29 October 2008 (13 days after the conclusion of the hearing and 19 days after his interlocutory decision was given on the admissibility of the disallowed evidence), he again gave reasons for rejecting the disallowed evidence of Dr Van Rooijen and Dr Varnava.

181 In relation to Dr Van Rooijen's statement, his Honour said (at [65]): "Such evidence … was in the nature of expert opinion and had not been served in accordance with the rules. Since Dr Van Rooijen had no recollection of having examined the 2006 mammogram, the evidence could only be a reconstruction and would involve some speculation. The other problem was that to which I have already adverted, ie the evidence would inevitably involve some element of ex post facto exculpatory justification for what had occurred. I concluded that in all the circumstances such evidence would be unreliable and that it would be unfair to the plaintiff to admit it." 182 His Honour stated (at [70]) that his reasons for rejecting the evidence of Dr Varnava were the same as for Dr Van Rooijen. 183 In these passages his Honour referred for the first time, expressly, to the failure of the appellant to serve the expert testimony of Drs Van Rooijen and Varnava in accordance with the rules. 184 In argument on appeal, Mr Menzies submitted that this Court should have regard to all the reasons given by his Honour for rejecting the evidence. In effect, this was a concession against the appellant's interest. Mr Toomey raised no objection to this approach. 185 In summary, having regard to all the reasons his Honour gave from time to time, he rejected the disallowed evidence (on the basis that it was expert evidence) on the following grounds:

(a) The two radiologists had no independent recollection of the examining the relevant mammograms.

(b) It would be unfair and unreliable to allow the two radiologists "to bring to bear [their] current observations and understanding of what's happening and say, well, that must have been how my mind worked two years ago".

(c) It would be unreliable (and unfair to Mrs O'Gorman) to allow persons whose conduct is being directly attacked or criticised to provide expert evidence to justify their conduct (as that evidence would inevitably involve some element of ex post facto exculpatory justification).

(d) The matters referred to above do not go to weight but to admissibility.

(e) The evidence was in the nature of expert evidence and had not been served in accordance with the rules.

The nature of the evidence of the radiologists 186 Opinion evidence based on specialised knowledge requiring specified training, study or experience in a field in which the witness is an expert is expert evidence: Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305; (2001) 52 NSWLR 705 per Heydon JA (at [85], 743-744). I agree with Hoeben J that the rejected evidence fell into this category and was expert evidence. 187 Part of the rejected evidence amounted to expert opinion evidence and part was "the evidence of a highly qualified person directed to educating the tribunal as to a matter which is beyond its expertise": Cross on Evidence (loose-leaf) (at [29020]). As the learned authors explain, evidence of this kind, although not opinion evidence, is expert evidence: "A chemist for example may be called to explain how or why a drug operates on the human body in a certain way. An expert may 'identify facts which may be obscure or invisible to a lay witness.' The same is true of evidence about 'how a complex piece of equipment works … or what happens when a car skids'. That testimony depends on inference no more than does that of the despatch clerk who describes the bureaucratic process that an organisation follows when it receives an order to supply goods."

The relevance of the fact that the two radiologists had no memory of the 2006 examinations 188 At trial, as I have noted, the appellant sought to tender the disallowed evidence on the alternative basis that it was direct evidence of fact and not expert testimony. Hoeben J rejected the disallowed evidence tendered on this alternative basis on the ground that the witnesses had no memory of what had occurred when they examined the mammograms in March 2006. As his Honour observed, they did not know what their states of mind were when, in 2006, they examined the mammograms. 189 I agree, with respect, with his Honour's decision in this regard. The radiologists' recollection of what they had done and thought in 2006 was relevant to evidence of fact, and as they had no memory of these matters, they could not give such evidence. 190 In my opinion, however, the fact that the radiologists did not know what they saw and thought when they examined the mammograms in 2006 was not a valid reason for rejecting their expert evidence. As experts, they were entitled, later, to instruct themselves on the relevant facts by examining the relevant mammograms to express an opinion as to what the mammograms revealed. Provided they had examined the relevant mammograms before the trial, their memory of what had actually occurred in 2006 was irrelevant to the expert evidence they sought to give.

The failure to serve the statements in accordance with the UCPR 191 As I have attempted to demonstrate, it is far from clear that, during the trial (as opposed to when delivering his written reasons for judgment), the appellant's failure to serve their statements as expert reports under the UCPR was a ground that Hoeben J relied on for rejecting the disallowed evidence of Drs Van Rooijen and Varnava. Not only did his Honour, at that particular stage, not make any express reference to the rules of court, nor did Mr Bartley. In fact, Mr Bartley at no time relied on any contravention of the rules of court in opposing the disallowed evidence. 192 The only possible basis for contending that, in the course of the adducing of evidence, his Honour had the appellant's non-compliance with the UCPR in mind as a ground for rejection, is his Honour's reference to the "earlier debate" that he made when giving his reasons for rejecting Dr Van Rooijen's disallowed evidence, coupled with his Honour's remark, when rejecting Dr Varnava's disallowed evidence, that his rulings were "consistent with the earlier debate we have had". 193 Relying on the matters set out in the previous paragraph, Mr Toomey submitted that, prior to delivering his reasons for judgment, his Honour, impliedly, indicated that non-compliance with the UCPR was one of his reasons for rejecting the disallowed evidence. This submission formed the basis of the further submission that, as - during the trial - the appellant did not seek to obtain his Honour's leave to serve the disallowed evidence in the form of experts' reports, it cannot now complain of the rejection of that evidence. 194 I would not uphold these submissions. 195 Firstly, in my opinion, the uncertainty (to which I have referred) of what his Honour meant when referring to the "earlier debate" (that is, in the context of what precisely had occurred in rejecting the disallowed evidence of Dr Stephen and Dr Van Rooijen), the fact that Mr Bartley did not during the leading of evidence rely on non-compliance with the rules, and the reasons his Honour gave when spelling out "exactly" why he rejected the disallowed evidence, compel the inference that, when his Honour, during the leading of the disallowed evidence, rejected it, he did not indicate that he was doing so for reasons that included non-compliance with the UCPR. 196 Secondly, even if the view expressed in the previous paragraph be incorrect, due regard must be had to the strength and firmness of his Honour's views as to firstly, the unfairness that would result from allowing the disallowed evidence, and secondly, the lack of reliability of that evidence. Any responsible counsel, who had unsuccessfully tendered that evidence, would conclude from the way his Honour had expressed himself, that it would be counter-productive and a waste of time and costs to apply once more to adduce that evidence merely on the basis that it could be redrafted and couched in the form required by the UCPR. In my opinion, Mr Menzies was entitled to take the view that there was no point in the appellant applying for leave to serve the disallowed evidence in the form of an expert's report as the UCPR rules require. 197 During argument on appeal there was some debate as to whether, when Hoeben J referred in [65] of his reasons to Dr Van Rooijen's evidence being "in the nature of expert evidence" and that "it had not been served in accordance with the rules", his Honour was referring to all the rules that had a bearing on expert evidence or whether he was confining himself to those rules relating to service of experts' reports (Pt 31 r 28). His Honour's remark is ambiguous. 198 In all the circumstances, it is difficult to ascertain, reliably, what precise aspect of the UCPR his Honour had in mind in referring to the rules in [65] of his reasons. In my view, his Honour's reference to the rules should not be regarded as incorporating every aspect of the UCPR that bears on expert evidence. 199 Irrespective of whether the conclusion in the last paragraph is correct, one thing is clear. That is, whatever weight his Honour attached to the failure to serve the evidence in question in accordance with the rules, his Honour's views as to the reliability of that evidence and the unfairness involved in allowing a person who had an interest in the proceedings to give expert evidence were, overwhelmingly, the factors that led his Honour to reject the evidence. The relevance of the Code of Conduct under Pt 31 r 23 200 During the course of argument there was some discussion as to whether expert witnesses in the position of Drs Van Rooijen and Varnava would be able to comply with the Code of Conduct applicable to expert witnesses under Pt 31 r23. 201 The duties that expert witnesses owe to the Court are set out in Pt 31 r 23 and the Code of Conduct in Sch 7 of the UCPR. Clause 2 of the Code of Conduct states: "2 General duty to the court

(1) An expert witness has an overriding duty to assist the court impartially on matters relevant to the expert witness's area of expertise.

(2) An expert witness's paramount duty is to the court and not to any party to the proceedings (including the person retaining the expert witness).

(3) An expert witness is not an advocate for a party." 202 In National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) [1993] 2 Lloyd's Rep 68, Creswell J set out the following exposition of duties owed by expert witnesses to the Court (at 81): "The duties and responsibilities of expert witnesses in civil cases include the following: 1. Expert evidence presented to the Court should be, and should be seen to be, the independent product of the expert uninfluenced as to form or content by the exigencies of litigation ( Whitehouse v Jordan [1981] 1 WLR 246 at p 256, per Lord Wilberforce). 2. An expert witness should provide independent assistance to the Court by way of objective unbiased opinion in relation to matters within his expertise (see Polivitte Ltd v Commercial Union Assurance Co Plc [1987] 1 Lloyd's Rep 379 at p 386 per Mr Justice Garland and Re J [1990] FCR 193 per Mr Justice Cazalet). An expert witness in the High Court should never assume the role of an advocate. 3. An expert witness should state the facts or assumption upon which his opinion is based. He should not omit to consider material facts which could detract from his concluded opinion ( Re J sup ). 4. An expert witness should make it clear when a particular question or issue falls outside his expertise. 5. If an expert's opinion is not properly researched because he considers that insufficient data is available, then this must be stated with an indication that the opinion is no more than a provisional one ( Re J sup ). In cases where an expert witness who has prepared a report could not assert that the report contained the truth, the whole truth and nothing but the truth without some qualification, that qualification should be stated in the report ( Derby & Co Ltd and Others v Weldon and Others , The Times, Nov 9, 1990 per Lord Justice Staughton). 6. If, after exchange of reports, an expert witness changes his view on a material matter having read the other side's expert's report or for any other reason, such change of view should be communicated (through legal representatives) to the other side without delay and when appropriate to the Court. 7. Where expert evidence refers to photographs, plans, calculations, analyses, measurements, survey reports or other similar documents, these must be provided to the opposite party at the same time as the exchange of reports (see 15.5 of the Guide to Commercial Court Practice)." 203 This "admirable resume" of duties and responsibilities was endorsed by the English Court of Appeal: National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) (No 1) [1995] 1 Lloyd's Rep 455 at 496. In Makita Heydon JA remarked that the Code of Conduct relating to expert witnesses under the New South Wales Rules of Court was influenced by the duties identified in The Ikarian Reefer. 204 As far as I can ascertain, the notion that expert witnesses owe a duty to the court was recognised for the first time in The Ikarian Reefer. Witnesses stand in a different position to lawyers. The public interest in the administration of justice is the source of duties that lawyers owe to the court: Rondel v Worsley [1969] AC 191 at 227 per Lord Morris. Since time immemorial the courts have assumed the inherent power to impose such duties: Myers v Elman [1940] AC 282 at 302 per Lord Atkin. The underlying principle is that "the court has a right and duty to supervise the conduct of those appearing before it, and to visit with penalties any conduct of a lawyer which is of such a nature as to defeat justice in the very cause in which he is engaged professionally": Myers v Elman at 319 per Lord Wright. Whether at common law the court has like powers over expert witnesses is open to question. 205 Although the effect of Pt 31 r 23 is that, by subsidiary legislation, expert witnesses owe a duty to the court, the content of that duty, and the powers of the court in enforcing that duty, are yet to be determined finally. 206 In FGT Custodians Pty Ltd (formerly Feingold Partners Pty Ltd) v Fagenblat [2003] VSCA 33 at [15] Ormiston JA (Chernov and Eames JJA agreeing) said: "[A]ll that has been said, particularly in recent years, about the desirability of expert witnesses providing independent evidence by way of opinion to the courts should be seen as expressions of the ideal manner in which expert witnesses should go about their tasks and the resultant opinions which those witnesses should strive to express. With but a few minor exceptions, none of them should be treated as stating principles of the law of evidence but they should be seen rather as admonitions to those who would give expert evidence, especially as to the way they should prepare and present that evidence to courts, if they and their clients wish it to be acted upon. Some of the statements are also directed to the ways in which courts prefer from time to time to direct the manner in which such evidence should be given, whether, for example, by way of appointment of so-called court experts or by directions requiring experts to consult and the like. However desirable these new rules and protocols may be, they cannot establish changes to the principles underlying the law of evidence, for they can do no more than change the relevant practice in particular jurisdictions, albeit that the form of such rules may involve an effective change in some of those rules under and by the authority of the relevant delegated powers invested in particular rule-making bodies." 207 Ormiston JA explained Cresswell J's position in The Ikarian Reefer as follows (at [17]): "Cresswell J was dealing, as may be seen from the report, with witnesses called pursuant to guidelines laid down in the 1993 Guide to the Commercial Court Practice, which were in part directed to restricting the number of expert witnesses who could be called. It is again significant to note that the seven precepts laid down by his Lordship in that case were not directed to competence or admissibility in general but were introduced by the words: 'The duties and responsibilities of expert witnesses in civil cases include the following ...'. I should treat them, therefore, as essentially precepts or ideals towards which expert witnesses should strive rather than the basis of any new exclusionary rules. Even the Civil Procedure Rules 1998 (Eng) which flowed from the seemingly radical recommendations of Lord Woolf's Final Report on Access to Justice July 1996, were not expressed in terms denying competence or admissibility, but merely in terms of a 'duty' to aid the Court … ." 208 Consistently with Ormiston JA's views in ASIC v Rich [2005] NSWSC 149 at [254] Austin J described Cresswell J's observations as being, in part, "moral exhortations rather than legal requirements". 209 In Kirch Communication Pty Ltd v Gene Engineering Pty Ltd [2002] NSWSC 485 Campbell J said: "It was, presumably, because rules for admissibility of expert evidence contained in the Evidence Act did not go far enough towards having only unbiased considered and current opinions put before the court as expert evidence that Part 36 Rule 13C was inserted into the Supreme Court Rules in January 2000." 210 I accept that the rules to which his Honour was referring and the current equivalent of those rules impose more stringent duties on expert witnesses than did the common law, as his Honour implies. But, his Honour in that observation was not saying, with respect, that the rules render inadmissible expert evidence of witnesses who have an interest in the proceedings. 211 Irrespective of the precise content of the duties to the court now owed by expert witnesses under pt 31 r 23, there is no reason why expert witnesses who have a material interest in the proceedings in which they are to testify should not be able to comply with those duties. Nothing in the content of those duties, as described by Cresswell J in the Ikarian Reefer, suggests that an honest expert witness who has a material interest in the proceedings would be unable to comply with the requirements imposed thereby. For example, such a material interest would not render it impossible for the expert to present evidence to the Court that is the independent product of the expert - uninfluenced as to form or content by the exigencies of litigation, or for the expert to provide independent assistance to the Court by way of objective unbiased opinion in relation to matters within his or her expertise, or for the expert to refrain from assuming the role of an advocate. Such an expert might well be able to give truthful evidence, to ensure that the court is fully informed of his or her reasoning process, and to present evidence without misleading the court or concealing any relevant facts from the court. Whether the expert does so is a matter to be tested in cross-examination. 212 I therefore conclude that there is nothing in the UCPR that prevents a person in the position of Drs Van Rooijen and Varnova from complying with the code of conduct applicable to expert witnesses.

Are parties to litigation, or their employees prohibited from giving expert evidence in their own favour? 213 In FGT Custodians Pty Ltd (formerly Feingold Partners Pty Ltd) v Fagenblat Ormiston JA said: "[E]vidence is frequently admitted as to the way in which vehicles will be likely to move in certain specified circumstances, if the witness is suitably qualified by experience or training to give expert evidence on the subject. Thus, so long as one avoids the pitfalls of attempting to call such evidence in circumstances such as were described in Clark v Ryan [1960] HCA 42; (1960) 103 CLR 486, it is possible that persons having long experience in driving or observing articulated vehicles may give evidence of the way they would be likely to move when rounding a curve or in other circumstances, such as was in fact admitted by the High Court from an expert witness in Weal v Bottom (1966) 40 ALJR 436. There should be no reason why a party, if a highly experienced driver, could not give such evidence, subject to the risk that he or she may be subject to the usual comment. " (My underlining) 214 His Honour continued (at [24]): "It is sufficient to say that in large numbers of commercial disputes, one party or the other frequently has particular expertise of a kind where it is frequently, but often only incidentally, necessary to qualify the witness to give expert evidence as to some particular aspect of that trade or business. It would be remarkable if one had to obtain another expert from a competitor or even from outside the country to prove particular aspects of that evidence, whether related to trade usages or technical mechanical processes or whatever. Such evidence can surely be given by a party, or by an officer of a corporate party, and the fact that it comes from such a witness, qualified if required as an expert, should be a matter merely for comment by counsel in argument and a matter of weight for consideration by the judge in reaching his ultimate decision. " (My underlining) 215 The same view has been expressed in several other cases. 216 In Fortson Pty Ltd v Commonwealth Bank of Australia [2008] SASC 49; (2008) 100 SASR 162 the bank retained a property valuer to give expert opinion evidence at trial. Following hearing of the appeal the case was subsequently remitted for the determination of damages. The same valuer was retained to give evidence in the rehearing. By that time, however, the valuer had in fact become an employee of the bank. Debelle J (with whom Doyle CJ and Bleby J agreed) stated (at [114], 192): "There will be occasions when the expert will, for some reason, not be entirely independent of the party calling the expert. That does not have the consequence that the evidence of the expert is inadmissible. The issue is whether Burton had the competence to give this valuation evidence. Plainly, he was competent to do so by virtue of his qualifications and his inspection of the hotel property. His evidence was of probative value. If evidence is of some, albeit slight, probative value, it is admissible unless some principle of exclusion comes into play to justify withholding from the court's consideration: Festa v R [2001] HCA 72; (2001) 208 CLR 593 at [14] per Gleeson CJ. There is no principle that disqualified Burton from giving evidence. The issues were examined at length in FGT Custodians Pty Ltd v Fagenblat [2003] VSCA 33, by Ormiston JA, with whom Chernov and Eames JJA agreed. Ormiston JA concluded at [29]: 'However desirable it may be, as a matter of common sense in the presentation of a party's case, that an expert witness be seen to be independent, there is therefore no authority requiring this Court to hold that an "interested" expert's evidence be rejected because of a "perception" that the witness might favour the party seeking to adduce that evidence'. I respectfully agree. In Flavel v South Australia [2007] SASC 50; (2007) 96 SASR 505, Bleby J also agreed with that reasoning and noted other decisions to like effect in the Supreme Court and the Court of Appeal in New South Wales as well as in the Federal Court of Australia. I respectfully agree with the reasons of Bleby J for concluding that the decision in Liverpool Roman Catholic Archdiocese Trustees Inc v Goldberg (No 2) [2001] 1 WLR 2337 should not be followed. As Bleby J noted, that decision was also disapproved by the Court of Appeal in R (Factortame Ltd) v Secretary of State for Transport, Local Government and the Regions (No 2) [2002] EWCA Civ 932; [2003] QB 381. The fact that Burton was employed by the Bank did not mean that he could not be called as an expert." 217 In Li v R [2003] NSWCCA 290; (2003) 139 A Crim R 281 the court considered whether the potential bias of an expert was a matter going to weight or to admissibility of evidence. In my reasons (with which Whealy and Howie JJ agreed) I said (at [71]): "In my opinion all of the arguments raised in relation to Sergeant Lee concerned matters of weight and were essentially matters for the jury. Most of the points made are repetitive of those concerning Mr Chan, and it is not necessary to discuss them again. I would add that the shortness of the passages examined by Sergeant Lee are plainly matters of weight and would not give rise to any unfairness. The risk of bias (unconscious or otherwise) is no reason not to admit evidence of an expert: FGT Custodians Pty Ltd v Fagenblat [2003] VSCA 33 (Ormiston JA, Chernov and Eames JJA concurring); Collins Thomson v Clayton [2002] NSWSC 366 per Austin J, and Kirch Communications Pty Ltd v Gene Engineering Pty Ltd [2002] NSWSC 485 per Campbell J. See also paper delivered by Heydon J entitled 'Comments on May LJ's Paper' at Supreme Court Conference, 22 August 2003." 218 In Field v Leeds CC (2000) 32 HLR 618; [1999] CPLR 833 (at 621), Lord Woolf MR expressed the same opinion in the context of the English Civil Procedure Rules: "The issue, which the City understood that this appeal to this court involves, is whether under the CPR it is inappropriate for an expert to be called who is an employee of the City, as opposed to an expert who is not so employed. If that is the issue which arises on this appeal, then it is a non-issue. Mr Luba, who appears on behalf of the tenants, would accept that if an expert is properly qualified to give evidence, then the fact that he is employed by a local authority would not disqualify him from giving evidence. In my judgment, Mr Luba is absolutely correct to accept that position."

Waller LJ said, similarly (at 623): "The question whether someone should be able to give expert evidence should depend on whether, (i) it can be demonstrated whether that person has relevant expertise in an area in issue in the case; and (ii) that it can be demonstrated that he or she is aware of their primary duty to the court if they give expert evidence."

May LJ stated (at 624): "As to questions of opinion and generally, I entirely agree with my Lord, the Master of the Rolls, that there is no overriding objection to a properly qualified person giving opinion evidence because he is employed by one of the parties. The fact of his employment may affect its weight but that is another matter." 219 In the circumstances, I consider that Hoeben J erred in deciding that the expert evidence of Drs Van Rooijen and Varnava was inadmissible merely because they were materially interested in the proceedings, would tend to give exculpatory evidence, and, for these reasons, their evidence would be inherently unreliable. Essentially, these matters went to weight and not admissibility, and in my view, his Honour, with respect, erred in coming to the contrary view.

The relevant provisions of the Evidence Act 1995 (NSW) 220 Section 56 of the Evidence Act provides: " 56 Relevant evidence to be admissible Except as otherwise provided by this Act, evidence that is relevant in a proceeding is admissible in the proceeding.

Evidence that is not relevant in the proceeding is not admissible." 221 Undoubtedly, the disallowed evidence was relevant. The respondent does not contend to the contrary. The only section to which reference was made on the respondent's behalf that could render the evidence in question inadmissible is s 135. This provides: " 135 General discretion to exclude evidence The court may refuse to admit evidence if its probative value is substantially outweighed by the danger that the evidence might:

(c) cause or result in undue waste of time". 222 It is arguable that Hoeben J intended to rely on s 135(a), although his Honour did not mention the section. 223 The difficulty with any reliance on s 135(a) is that, as I have mentioned, the predominant grounds on which Hoeben J rejected the evidence was the inherent unfairness of allowing persons in the position of the radiologists to give expert evidence and the inherent unreliability of that evidence. While the notion of unfairness might encompass "unfairly prejudicial" within the meaning of s 135(a), that is no answer to his Honour's decision that the inherent unreliability of the evidence meant that it should not be admitted. 224 In my view, irrespective of whether his Honour was intending to exercise a discretion under s 135 in rejecting the disallowed evidence, his view that an important ground on which the evidence should be rejected was its unreliability was a material error of legal principle. 225 I would add that, to the extent that his Honour's decision amounted to a finding that admitting the evidence would be unfairly prejudicial to the respondent, his Honour erred, in my opinion, in failing to take into account the unfairness to the appellant in preventing the persons (for whose conduct the appellant was vicariously liable) from explaining and defending their conduct.

Should a retrial be ordered? 226 Pt 51 r 53 provides that the Court must not order a retrial on the ground of improper rejection of evidence unless it appears to the Court that some substantial wrong or miscarriage has been thereby occasioned. 227 I have mentioned that the "fundamental issue" that in effect determined the question of liability was the resolution of the dispute between Dr Kitchener and Associate Professor Osborne as to whether there had been a significant change in the size of the mass shown on the 2006 mammogram. Hoeben J explained (at [96]) that in determining this issue he had taken into account his "assessment of the respective witnesses". His Honour was more impressed with the demeanour of Dr Kitchener and the way he presented his evidence than he was with Associate Professor Osborne (see in this regard his Honour's comments at [96] and [97].

228 In principle, once demeanour is a significant factor in determining the issue on which the question of liability turns, the rejection of witnesses whose testimony supports the witness whose evidence was not so accepted has the potential of resulting in a miscarriage. That is because, subject to issues of cogency of the rejected evidence, the conclusion is inevitable that the rejected evidence could well lead to a different result. Thus, in considering whether the erroneous rejection of evidence should give rise to a retrial, careful consideration must be given to cogency of the rejected evidence. 229 I do not think that Dr Van Rooijen's evidence that was rejected would have had any material affect on the result. That is because in her statement she did not state that she had inspected the 2002 or 2004 mammograms. I take into account her evidence that she believed that "after viewing the 2002 and 2006 mammograms" she would have noted Mrs O'Gorman's history" was admitted. When that testimony is read in context, however, it is apparent that Dr Van Rooijen's reference to viewing the 2002 mammogram is something she believed she "would have done" in 2006, not something she in fact did in preparation for giving her expert opinion. In other words, she assumed, from her past practice, that in 2006 she would have examined the 2002 mammogram. This does not inspire any confidence that at the time of the trial she had a proper appreciation of what the 2002 mammogram showed. After all, she had no independent memory of the examination she carried out in 2006. 230 Thus, Dr Van Rooijen's evidence in paragraph 27 of her statement that the lesion in the left breast "was present over a four year period" was not supported by evidence that she independently recalled reviewing the 2002 mammogram. For that reason, in my opinion, Dr Van Rooijen's evidence that the lesion was present for that period, and that that feature, together with other matters, meant that she correctly determined that Mrs O'Gorman did not need to be recalled, was not admissible - let alone cogent. 231 Dr Varnava's evidence, however, falls into a different category. He stated (in paragraph 19 being evidence rejected by his Honour) that he reviewed the 2002 films "for the purposes of this statement". In evidence admitted by his Honour (paragraph 25) and other evidence that his Honour rejected (paragraph 26), Dr Varnava made it plain that he reviewed the 2004 films in 2008. Thus, Dr Varnava's assertion that he maintained his "interpretation of the plaintiff's 2006 mammogram as 'normal' rather than requiring further assessment" was properly supported by facts set out in his statement. 232 Mr Toomey, in resisting the proposition that Dr Varnava's rejected testimony was significant, drew attention to the fact that Dr Varnava conceded that the 2006 mammogram indicated an increase in the mass shown in the 2004 mammogram from 2.6 cm to 3.0 cm. He submitted that this was "clearly a linear measurement", involving only one dimension. He argued that if one applied the appropriate mathematical formula applicable to a sphere (and he contended that the mass was a sphere) the increase in the mass would be 78 per cent. I would not accept this argument. It was not proved that the mass was a sphere, the appropriate formula for calculating the percentage increase in the mass as a whole was not in evidence, and Dr Varnava's statement that the mass had increased to 3.0 cm was part of evidentiary material in which Dr Varnava said that the 2006 mammogram was normal. In these circumstances, this Court is not in a position to find that the effect of Dr Varnava's evidence about the increase from 2.6 cm to 3.0 cm amounted to an increase in the mass of 78 per cent. 233 In paragraph 31 of his statement (that was rejected) Dr Varnava gave eight reasons for his conclusion that the 2006 mammogram was normal. As this evidence was not before his Honour, he did not consider how these reasons affected the evidence of Dr Kitchener.

234 In all the circumstances, I am satisfied that Dr Varnava's disallowed evidence had the capacity to bring about a different result in the case. 235 I would uphold the appeal on the issue of negligence and order a retrial in that regard.

The cross-appeal 236 The respondent cross-appeals against the assessment of damages on two grounds. The first ground asserts that Hoeben J erred in deducting from the damages awarded in respect of the respondent's loss of earning capacity in the "lost years" the full amount of her mortgage payments (cf James Hardie & Co v Roberts [1999] NSWCA 19; (1999) 47 NSWLR 425 at [44] to [47]). The second ground concerns the award for non-economic loss. His Honour found that the respondent's injuries amounted to 55% of a most extreme case. The respondent submitted that this amount was "erroneously low".

237 As regards the first ground, the respondent accepted that, had she been renting her home, there could be "little argument" against the whole of the rent being deducted from her putative future earnings. The respondent pointed out, however, that in making her mortgage payments, she was not only paying interest on the mortgage but reducing the capital sum she borrowed to purchase her home. The respondent submitted that in so doing she was "increasing the extent of her equitable interest in the asset". She submitted that the mortgage payments she made exceeded the payments necessary for her to make in order to exercise her earning capacity. On this basis, she submitted that those parts of the mortgage payments that reduced the capital amount of the loan secured by the mortgage should not be deducted from her future earnings. 238 The difficulty that faces the respondent on this argument is that no evidence was adduced as to the respective amounts she paid in respect of capital and interest when she paid her mortgage instalments. The appellant submitted that: "There being no breakdown between capital and income components in the evidence (or evidence of what the market rent for the premises would be), his Honour was correct to make a deduction of the entire amount, in effect equating it to rent". 239 I accept the appellant's submission that, in the absence of evidence that would enable the extent of any increase in the respondent's interest in her home to be calculated, his Honour correctly deducted the entire amount of mortgage payments (thereby equating the mortgage payments, in effect, with rent). Accordingly, I would not uphold this ground of appeal. Mr Toomey submitted that should this ground be rejected on the absence of evidence ground, the matter should be remitted for further evidence on the point. I do not accept this submission. It was for Mrs O'Gorman, as plaintiff, to lead the evidence necessary to establish the case. She did not do so. Thus the cross-appeal must fail on this ground. 240 As regards the second ground of appeal, the respondent does not submit that his Honour made any particular error of principle when basing the award for non-economic loss on the finding of 55% of a most extreme case. I accept that his Honour's award was significantly towards the lower end of the scale, but I am not persuaded that it was outside the bounds of a reasonable discretion. I would not uphold this ground. 241 In the circumstances I would not uphold the cross-appeal.

Conclusion 242 As I have stated, the appeal should be upheld and a retrial ordered on the issue of whether the appellant was negligent as alleged. Negligence is a separate and discrete question. No issue of credibility involving causation or the assessment of damages bears on the issue of negligence. The issue of causation involves facts that are substantially common ground and there is no need to agitate that issue again. The assessment of damages is an entirely separate issue and, likewise, there is no need for it to be the subject of a further trial. Thus, bearing in mind what was said by Gleeson CJ in Waterways Authority v Fitzgibbon [2005] HCA 57; (2005) 221 ALR 402 at [15], [19] and [20] (with which McHugh, Gummow and Hayne JJ agreed), I would nevertheless limit the issue in the retrial to the question of negligence.

(c) The matter is remitted to the Common Law Division of the Supreme Court for a re-trial on the issue of negligence.

(d) The respondent pay the appellant's costs of appeal.

(e) The respondent be entitled to a certificate under the Suitors' Fund Act 1951 if otherwise entitled.

(f) The costs of the trial before Hoeben J be costs in the cause.

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