Murray v Shillingsworth

LEGISLATION CITED: District Court Act 1973 Workers Compensation Act 1987

Adelaide Stevedoring Co Ltd v Forst (1940) 64 CLR 538 Ambulance Service New South Wales v. Daniel (2000) 19 NSWCCR 697 Azzopardi v. Tasman UEB Industries Ltd (1985) 4 NSWLR 139 Commonwealth v Amann Aviation Pty Ltd (1991) 174 CLR 64 EMI (Australia) Ltd v Bes (1970) WCR 114 Fink v Fink (1946) 74 CLR 127 G v. H (1994) 181 CLR 387 CASES CITED: Hevi Lift (PNG) Ltd v Etherington [2005] NSWCA 42 Jones v Dunkel (1959) 101 CLR 298 Liverpool/Fairfield Disabled Persons Resource Service Inc v. Liew [2002] NSWCA 31 Mercer v Australia and New Zealand Banking Group Ltd [2000] NSWCA 138 Pickwell v. Cotswold Australia Pty Ltd (2001) 22 NSWCCR 654 Raines v. Bayebb Pty Ltd (2002) 23 NSWCCR 687 Seltsam Pty Ltd v. McGuiness [2000] NSWCA 29 WorkCover Authority of New South Wales v Walsh [2004] NSWCA 186

PARTIES: Graham Murray (Appellant) Ronald Shillingsworth (Respondent)

COUNSEL: SG Campbell SC, Ms DR Moore (Appellant) M Daley (Respondent)

SOLICITORS: Hunt & Hunt (Appellant) Brydens Law Office (Liverpool) (Respondent)

IN THE SUPREME COURT OF NEW SOUTH WALES COURT OF APPEAL CA 40187/06 RJ4094/2002

HODGSON JA SANTOW JA EINSTEIN J

Wednesday 20 December 2006 MURRAY V SHILLINGSWORTH

The respondent suffered a cerebral haemorrhage in the course of his employment working for the appellant as a cotton chipper on 13 January 1997. The respondent unsuccessfully brought proceedings in the former Compensation Court seeking weekly benefits compensation and lump sum compensation pursuant to s 66 and 67 of the Workers Compensation Act 1987. The respondent successfully appealed to this Court, setting aside the award. The matter was remitted for rehearing in the District Court. On the rehearing, Bishop J entered a verdict in favour of the respondent. The appellant appealed on the following grounds:

1. The trial judge misdirected himself as to the onus of proof.
2. The trial judge failed to provide adequate reasons for accepting one medical hypothesis as to the aetiology of the respondent's stroke over the others.
3. The trial judge misdirected himself as to the interplay between the requirement of "contributing factor" in s 4(b)(ii) and "substantial contributing factor" in s 9A Workers Compensation Act 1987.
4. The trial judge erred in his interpretation of s 9A so that its burden falls unevenly in the same matter, which made it more difficult to satisfy s 9A in a case of injury simpliciter than in the case of injury by way of aggravation or acceleration of pre-existing disease.
5. The trial judge erred in his application of s 9A to the facts of the case and failed to have any regard at all to the factors referred to in s 9A(2).
6. The trial judge erred in finding that the employment concerned was a significant contributing factor to the respondent's injury when there was no evidence that the employment concerned caused additional material dehydration; or alternatively there was no evidence that any additional work caused dehydration made a difference to the outcome. HELD: per Einstein J (Hodgson and Santow JJA agreeing)

1. The trial judge was entitled to accept the evidence of Dr Stening, expert for the respondent, in support of the thrombotic haemorrhage theory: at [47].
2. The trial judge discharged his obligation to give adequate reasons: at [50-51].
3. The question of whether employment is a substantial contributing factor is one of fact: at [53].
4. The requirement that the employment be a contributing factor to the "injury" is not equivalent to the expression "arising out of the employment": at [57].
5. The question of what is "substantial" is left to the personal judgment of the individual judge according to the circumstances of each case: at [58].
6. There was no error in the trial judge's approach to the question of construction upon the basis that the case was put as an acceleration or aggravation or deterioration of a pre-existing condition in which the substantial contributing factor had to relate to the acceleration or aggravation and not to the underlying condition: at [64].
7. There were clearly facts proved which formed a reasonable basis for the definite conclusion justifying the finding that the employment concerned was a substantial contributing factor to the injury: at [65].

HELD: per Hodgson JA (Santow JA and Einstein J agreeing)

1. Where a court is faced with a number of competing hypotheses as to the cause of an injury, it may not always be a correct approach to proceed by rejecting in turn all but two of the hypotheses, and then selecting the more probable of those two: at [2].

1. Inferences can legitimately be drawn which depend in part, at least, on intuition: at [10].

1. Appeal dismissed.
2. Appellant to pay the respondent's costs of the appeal.

IN THE SUPREME COURT OF NEW SOUTH WALES COURT OF APPEAL CA 40187/06 RJ4094/2002

HODGSON JA SANTOW JA EINSTEIN J

Wednesday 20 December 2006 MURRAY V SHILLINGSWORTH Judgment 1 HODGSON JA: I agree with the orders proposed by Einstein J, and subject to what I say below, I agree substantially with his reasons. I would add some comments of my own. 2 In relation to the first ground of appeal, I would comment that where a court is faced with a number of competing hypotheses as to the cause of an injury, it may not always be a correct approach to proceed by rejecting in turn all but two of the hypotheses, and then selecting the more probable of those two. 3 Although I do not suggest that a court should assign mathematical probabilities to the hypotheses it is considering, the point can best be illustrated in terms of mathematical probabilities. If there are five hypotheses, and three have only 0.1 (10%) probability each, the more probable of the remaining two may have only a little over 0.35 (35%) probability: cf. G v. H (1994) 181 CLR 387, and my article "The Scales of Justice: Probability and Proof in Legal Fact-finding" (1995) 69 ALJ 731 at 744-746. 4 However, this point was not taken below or on appeal. In any event, in the present case the procedure adopted was I believe favourable to the appellant, because the least unlikely of the hypotheses thus disregarded would have supported the respondent's case that his injury was work-related; and in my opinion, in this case, if there were two hypotheses supporting the respondent's case, the respondent could have relied on the combined probability of both of them, without having to establish which one was correct: cf. 69 ALJ at 748-750. 5 On the basis on which the case was fought below and on appeal, there was a rational basis for the primary judge to accept the evidence of the treating specialist Dr. Stening, and the primary judge gave adequate reasons for doing so. 6 In relation to the grounds of appeal concerning s.9A of the Workers' Compensation Act 1987, there were two significant points argued. First, it was said that the reasons of the primary judge disclosed error, in that he drew an untenable distinction between the application of s.9A to an injury simpliciter, and its application to an aggravation of a pre-existing condition; and second, it was said that, having regard to the respondent's evidence that when he got hot he would have a drink of the water he took with him, the respondent's evidence could not establish that the employment contributed substantially to the dehydration which (on the primary judge's finding) triggered the injury. 7 As to the first point, I think there may be cases where the question of whether the employment was a substantial contributing factor is affected by whether one considers the work occurrence as an injury simpliciter or as an aggravation of a pre-existing condition. In some cases at least, where an injury simpliciter can be considered as having been contributed to by a pre-existing condition, the employment contribution to that injury could be diluted to that extent. However, if the same event can also be regarded as an aggravation of that pre-existing condition, then the employment contribution to the aggravation may not be diluted by the pre-existing condition (although the compensation would then be strictly limited to the effect of the aggravation). This seems to have been the view taken by the primary judge, and in my opinion he was not wrong in taking that view. 8 In my opinion however, even the aggravation in this case can be seen as contributed to by dehydration resulting from the previous day's consumption of alcohol, which I would not regard as part of the respondent's pre-existing condition. The question remains whether the primary judge was in error in holding that the work-related dehydration was a substantial contributing factor. In my opinion, the primary judge was correct to disregard the long history of smoking used by Dr. Stoodley to dilute the employment contribution, because that long history was part of what gave rise to the pre-existing condition. The evidence that the respondent would drink when he got hot did not, in my opinion, preclude an inference that the work described by the respondent increased his dehydration, and in my opinion the primary judge was justified in those circumstances in relying on the evidence of Dr. Stening and on that basis finding that the employment was a substantial contributing factor. 9 SANTOW JA: I agree with Einstein J and the additional observations of Hodgson JA. 10 As to Einstein J's observation about whether the trial judge impermissibly acted on his own "intuitive" reasoning, it should not be overlooked that inferences can legitimately be drawn which depend in part, at least, on intuition; cf Rich ACJ in Adelaide Stevedoring Co Ltd v Forst (1940) 64 CLR 538 cited by Einstein J. What is impermissible is to proceed by intuitive reasoning only in such a way as to render the conclusion merely speculative or idiosyncratic. This, I agree, the trial judge did not do. Even rigorous scientific reasoning may, however, contain an element of intuitive inference still awaiting scientific confirmation though with promising indications, such as in the acceptance of a particular assumption. 11 EINSTEIN J:

The state of these proceedings 12 The respondent to the present appeal brought proceedings before the former Compensation Court seeking weekly benefits compensation from 13 January 1997 and lump sum compensation pursuant to s 66 and 67 of the Workers Compensation Act 1987. 13 The first hearing took place before Ashford J who delivered a judgment on 17 December 2003 in the form of an award for the present appellant. 14 An appeal to this Court heard by Mason P, Sheller and Beazley JJ was allowed [2004] NSWCA 465, the Court setting aside the award and remitting the matter for rehearing in the District Court. 15 The second hearing took place before Bishop J who delivered a judgment on 27th February 2006. His Honour entered a verdict in favour of the respondent. The present appeal is brought from that decision. 16 The appeal is pursuant to s 142N of the District Court Act 1973. Hence the appeal is restricted to a party aggrieved by the award "in point of law or on a question as to the admission or rejection of evidence". 17 Whilst the present appeal treats and treats only, with the reasons given by Bishop J it is convenient to note the following non-contentious matters taken from the reasons given in the first appeal:

"[2] The appellant suffered catastrophic injury in the form of a left pontine cerebral haemorrhage that happened in the course of his employment working for the respondent as a cotton chipper on 13 January 1997. It was conceded that he was rendered totally incapacitated and entitled to maximum lump sum benefits should he establish his entitlement to an award.

[3] Unfortunately for the appellant, the law had been amended one day previously, by the insertion of s9A of the Workers' Compensation Act 1987 (the Act). That section provides: 9A No compensation payable unless employment substantial contributing factor to injury (1) No compensation is payable under this Act in respect of an injury unless the employment concerned was a substantial contributing factor to the injury.

(2) The following are examples of matters to be taken into account for the purposes of determining whether a worker's employment was a substantial contributing factor to an injury (but this subsection does not limit the kinds of matters that can be taken into account for the purposes of such a determination): (a) the time and place of the injury,

(b) the nature of the work performed and the particular tasks of that work,

(d) the probability that the injury or a similar injury would have happened anyway, at about the same time or at the same stage of the worker's life, if he or she had not been at work or had not worked in that employment,

(e) the worker's state of health before the injury and the existence of any hereditary risks,

(f) the worker's lifestyle and his or her activities outside the workplace. (3) A worker's employment is not to be regarded as a substantial contributing factor to a worker's injury merely because of either or both of the following: (a) the injury arose out of or in the course of, or arose both out of and in the course of, the worker's employment, (b) the worker's incapacity for work, loss as referred to in Division 4 of Part 3, need for medical or related treatment, hospital treatment, ambulance service or occupational rehabilitation service as referred to in Division 3 of Part 3, or the worker's death, resulted from the injury. (4) This section does not apply in respect of an injury to which section 10, 11 or 12 applies. [4] Section 9A added the requirement that "the employment concerned" be shown to have been "a substantial contributing factor to the injury" (see subsection (1)). The manner in which that requirement is to be determined is explicated positively and negatively in subsections (2) and (3). The scope of the section is discussed in Mercer v ANZ Banking Group Limited (2000) 20 NSWCCR 70 and subsequent cases in this Court and in the Commission…"

The respondent's case 18 The case advanced for the present respondent was that his employment on the day in question had contributed to the injury. It was contended that his work required him to repetitively bend, lift and twist and to perform strenuous physical work involving prolonged exposure to hot and hard working conditions.

The rehearing before Bishop J 19 The parties approached the rehearing by adducing some additional evidence at the same time as agreeing that the evidence given in the original proceedings was to be evidence on the rehearing. Additionally the parties reached an accommodation that in view of the catastrophic injury sustained by the respondent, he would not be recalled. As Bishop J. observed, the issue was sensibly compressed into a relatively narrow but extremely complex medical issue. 20 The reasons contain a compendious anthology of the differences in opinion expressed by the medical witnesses, accompanied by a detailed exposition of the precise issues treated with by those witnesses. A number of the medical witnesses had been required not only to summarise their own preferred position in terms of particular hypotheses, but also to state their opinion on the preferred position of other witnesses.

The grounds of appeal 21 The first ground of appeal is that the trial judge misdirected himself as to the onus of proof. 22 The second ground of appeal is that the trial judge failed to provide adequate reasons for accepting one medical hypothesis as to the aetiology of the respondent's stroke over the others. 23 The third, fourth and fifth grounds of appeal deal with suggested errors concerning the principled approach to:

i. the interplay between the requirement of "contributing factor" in s 4 (b) (ii) and "substantial contributing factor" in s 9A, each of the Workers Compensation Act 1987 [ "the third ground"]

• the contention being that the trial judge's interpretation would allow the burden to fall unevenly in the same matter;

• the contention being that on the trial judge's interpretation, it is more difficult to satisfy s 9A when it comes to injury simpliciter than in the case of injury by way of aggravation, acceleration etc of a pre-existing condition ["the fourth ground"] iii. the application of s 9A to the facts before the Court, the contention being that the trial judge failed to have any regard at all to the factors referred to in s 9A (2) [ "the fifth ground"] 24 The sixth ground of appeal contends that the trial judge erred in finding that the employment concerned was a significant contributor to the respondent's injury when:

i. there is said to have been no evidence that the employment concerned caused additional material dehydration; or alternatively;

ii. there is said to have been no evidence that any additional work - caused dehydration made a difference to the outcome.

Dealing with the first ground of appeal 25 The essence of this ground concerns whether or not the trial judge's decision was:

i. ultimately simply one of fact, or alternatively;

What is an error of law? 26 Whether or not an error constitutes an error of law is a matter informed by the decision of the Court in Azzopardi v. Tasman UEB Industries Ltd (1985) 4 NSWLR 139 at 156-7, as subsequently interpreted by the Court in Ambulance Service NSW v. Daniel (2000) 19 NSWCCR 697 at pp710-pp711; Raines v. Bayebb Pty Ltd (2002) 23 NSWCCR 687 at 698; Pickwell v. Cotswold Australia Pty Ltd (2001) 22 NSWCCR 654; Liverpool/Fairfield Disabled Persons Resource Service Inc v. Liew [2002] NSWCA 31. 27 In Azzopardi Glass JA at 156-157 said:

"Errors may be committed by a Workers' Compensation judge at any one of three points viz determining the facts by way of primary findings and inferences, directing himself as to the law and applying the law to the facts found. At the first stage the determination of facts by a reasoning process marred though it be by patent error, illogicality or perversity will, as has been said, never be vulnerable to attack as an error of law by an applicant for compensation. At the second stage any error made will by definition be an error of law. At the third stage when the law correctly stated is applied to the facts found in order to produce a conclusion error may intrude again. An erroneous conclusion that facts properly determined fail to satisfy a statutory test, for example, injury arising out of the course of employment, substantial interruption to journey, or failure to provide suitable employment will ordinarily be an erroneous conclusion of fact. It is only in marginal cases that the statutory test is satisfied or not satisfied as a matter of law, because no other application is reasonably open: Hope v. Bathurst City Council …Accordingly this Court will not entertain unexplained perversity of result as a ground for intervention although it will correct perverse or unreasonable applications of law to the facts found." 28 At 156B Glass JA said:

"It is also pointless to submit that the reasoning by which the court arrived at a finding of fact was demonstrably unsound as this would not amount to an error of law; R v. District Court of the Metropolitan District Holden at Sydney ; Ex parte White (1966) 116 CLR 644 at 654." [Cf Walsh v Vision Stream Pty Ltd [2004] NSWCA 104] 29 In Daniel's case Hodgson CJ in Eq dealt with a submission that it was very difficult to establish that there was no evidence and that it did not matter that the evidence was scanty or implausible, or even that the decision was perverse: the submission was that if there was any evidence at all on the point, there was no error of law. His Honour at [56] put the matter as follows:

In my opinion, Mr Hislop's submissions to some extent reflect a misunderstanding of what was decided in Azzopardi. In the main judgment in that case, that of Glass, JA, a clear distinction was drawn between the situation where the finding of fact in question is made in favour of a person bearing the onus of proof, and the situation where the finding of fact is made against the person bearing the onus of proof. In the former situation, the question is not whether there is any evidence at all on the point, but rather whether the evidence on the point is sufficient, in the sense that it is evidence which if fully accepted could properly base the finding of fact. The distinction is made clear in the following passage from the judgment of Glass, JA at p156: To the legally uninitiated there is a spurious validity in a submission that it was not open to the judge to find that the applicant was not injured since there was no evidence to that effect. If a respondent employer can argue a no evidence point, why cannot the applicant worker? The answer is, of course, that alleged insufficiency of evidence to prove a fact always raises a question of law but alleged sufficiency of evidence to the point of conclusiveness cannot, since it assumes that the evidence has been accepted. The party not bearing the onus puts an argument, which assumes against himself that the evidence has been accepted, but submits that it is not capable of establishing the fact. The party saddled with the onus on the other hand cannot assume in his favour that the evidence is or ought to be accepted since this trenches upon the liberty of the tribunal of fact to accept or reject any evidence. [emphasis added]

What are the legal requirements of proof on the balance of probabilities 30 These requirements were examined in Seltsam Pty Ltd v. McGuiness [2000] NSWCA 29 where Spigelman CJ put the matter as follows:

i. "There are cases in which medical science cannot identify the biological or pathological mechanisms by which disease develops. In some cases medical science cannot determine the existence of a causal relationship. Such a state of affairs is not necessarily determinative of the existence or non-existence of a causal relationship for purposes of attributing legal responsibility…In circumstances where the aetiology of a disease is uncertain, or subject to significant scientific dispute, the courts are not thereby disenabled for making decisions as to causation on the balance of probabilities." [at 93 - 94]

ii. "When assessing expert evidence on causation, the legal concept of causation requires the court to approach the matter in a distinctively different manner from that which may be appropriate in either philosophy or science, including the science of epidemiology. " [at 142]

iii. The commonsense approach to causation at common law is quite different from a scientist's approach to causation…an inference of causation for purposes of the tort of negligence may well be drawn when a scientist, including an epidemiologist, would not draw such an inference." [at 143] 31 Other authorities dealing with the different environments in which the requirements of the law and the ascertainment of scientific truth include:

i. HoIt le v. Hocking (1962) SASR 128 where Napier CJ found a causal connection established on the probabilities in circumstances where His Honour would have rejected such a connection if the requirement of the law was the ascertainment of scientific truth;

ii. Clarke v. Chandler (1984) Aust Torts Rep 80-631 where a causal connection was found even though the connection would probably not satisfy medical scientists; [Cf Bryden v. Chief General Manager of the Health Department (1986) Aust Torts Rep 80-075 where causation was found on the balance of probabilities though " a Nobel prize " awaits someone who could explain the link: Adelaide Stevedoring Co Ltd v. Forst (1940) 64 CLR 538 where the High Court held that while waiting for science to determine an issue " in the meantime act on our own intuitive inferences " per Rich ACJ] 32 Clearly the question posed by the first ground of appeal is as to whether the facts proved formed a reasonable basis for a definite conclusion affirmatively drawn, of the truth of which the tribunal of fact may be reasonably satisfied: cf Jones v Dunkel (1959) 101 CLR 298 at 305 per Dixon CJ. As his Honour observed: "[T]he law… does not authorise a Court to choose between guesses, where the possibilities are not unlimited, on the ground that one guess seems more likely than another with the others" 33 Difficulties of assessment are of course encountered in disparate areas including the assessment of damages. The principled approach to the difficulties and uncertainties involved in assessment of damages are in a sense not dissimilar from the issues presently before this Court. In that regard many authorities make clear that the mere fact that damages cannot be assessed without difficulty and uncertainty, does not relieve the court from its undoubted responsibility of attempting to assess those damages as best it can - per Deane J in Amann at 125 - who cites the following passage from the judgment of Dixon and McTiernan JJ in Fink v Fink (1946) 74 CLR 127:

'Where there has been an actual loss of some sort, the common law does not permit difficulties of estimating the loss in money to defeat the only remedy it provided for breach of contract, an award of damages.' [(1946) 74 CLR at 143] 34 However, Deane J went on in Commonwealth v Amann Aviation Pty Limited (1991) 174 CLR 64 to lay down one caveat of importance: 'There are, however, extreme cases in which curial procedures are simply inadequate to determine whether there was any real or significant chance that an alleged benefit would actually have been obtained but for the repudiation or breach of contract or to assess the intrinsic worth of a particular suggested "benefit… The nature of what would have been obtained if the contract had been performed may be so completely speculative that "it is quite impossible to place any value" upon it . . . In such cases, recovery of other than nominal damages by the plaintiff will depend either upon the applicability of principles of restitution to enable the direct recovery of a benefit obtained by the defendant or upon the presumption of value referred to in the following paragraph to enable the recovery of wasted expenditure.' [174 CLR at 125-126] [emphasis added] 35 The same point was made by Latham CJ and Williams J in Fink v Fink (supra at 134):

'The damage arising from loss of opportunity to obtain a benefit may be so dependent upon a number of contingencies as to be negligible ( Sapwell v Bass (1910) 2 KB 486).'

Returning to the trial judge's reasons 36 In my view there is no substance in the contention that a careful reading of the reasons of the trial judge demonstrates that his Honour effectively acted on his own intuitive reasoning in rejecting the hypothesis of the ruptured cavernoma as an explanation for the course of the respondent's left pontine haemorrhage or accepting the thrombotic hypothesis. 37 The contention rests upon the trial judge's reference to the following remarks of Herron CJ in EMI (Australia) Ltd v Bes (1970) WCR 114 at 119:

"It seems to me that bears out what I have concluded is the correct principle to apply, namely, that it is not incumbent upon the applicant upon whom the onus rests to produce evidence from medical witnesses which proves to demonstration that the applicant's contention is correct. Medical science may say in individual cases that there is no possible connection between the events and the death, in which case, of course, if the facts stand outside an area in which common experience can be the touchstone, then the judge cannot act as if there were a connection. But if medical science is prepared to say that it is a possible view, then in my opinion, the Judge after examining the lay evidence may decide that it is probable. It is only when medical science denies that there is any such connection that the Judge is not entitled in such a case to act on his own intuitive reasoning. It may be, and probably is, the case that medical science will find a possibility not good enough on which to base a scientific deduction, but Courts are always concerned to reach a decision on probability and it is no answer, it seems to me, that no medical witness states with certainty the very issue which the Judge himself has to try" (Red 77 Q to Y) 38 It is simply misconceived to suggest that the reference to these observations demonstrates that the trial judge acted on his own intuitive reasoning in his approach to weighing the factors in favour of and against the respective hypotheses put forward. As the authorities earlier referred to in these present reasons have made plain, the earlier treatment of principle by Herron CJ in some 36 years ago in EMI (Australia) holds as true today as it did at the time when the judgment was delivered.

The treatment of the respective theories on the cause of the haemorrhage 39 In its written submissions the respondent's counsel correctly observed that:

i. the mass of evidence before the Court disclosed a number of potential medical hypotheses as to the cause of the respondent's haemorrhage;

ii. whilst the medical evidence did not consistently adopt the following classification, the possibilities may be classified in the following manner: i. That the stroke was the result of coagulopathy/ vitamin deficiency due to the Respondent's drinking and diet.

ii. A cavernous haemangioma (cavernoma) being a pre existing abnormality.

iii. Transient increases of blood pressure acting upon an arterio venous malformation or other weakness.

iv. A hypertensive stroke differing from (iii) above because the underlying lesion was arthrosclerosis such that with hypertension the artery was prone to burst, including from exertion.

v. Thrombotic haemorrhagic stroke. 40 The first of these possibilities may be immediately put to one side for the reason that there was insufficient evidence to justify a finding accommodating this hypothesis and that the appellant did not ultimately press for any such a finding 41 Notwithstanding the significant medical support for the third and fourth possibilities [which were essentially identical, the main difference being that the underlying pathology in the hypertensive stroke option is atherosclerosis and hypertension, to which transient increases in blood pressure can act to cause a rupture of the blood vessel and hence a stroke and in the case of the former, there needed to be an area of weakness of some description, most probably an arteriovenous malformation], the trial judge found against this hypothesis and the appellant does not challenge these findings. 42 It is apparent that at the end of the day and following the additional evidence which had been given by Professor Stoodley and by Dr Stening during the second trial, in essence there remained for serious consideration only two possible mechanisms of haemorrhage as to how the stroke had occurred: these being the cavernoma theory and the thrombotic haemorrhage theory [arguably there were three such possible mechanisms because Professor Stoodley placed the thrombotic haemorrhage within his definition of the hypertensive stroke category] 43 This being the case the trial judge clearly had a difficult decision on causation to make. 44 The following overview summary [given by the respondent on the appeal] as to how the evidentiary and theoretical matters stood for the trial judge's consideration, comprises a fair representation of the overall position borne out by the materials before this Court:

i. A cavernoma is a benign inherited tumor which is apt to bleed from time to time (Red 73G). Professor Stoodley discussed the nature of a cavernoma in detail in his oral evidence (for example at Black 6E).

ii. The proponents of this theory were essentially Dr Matheson and Professor Stoodley for the Appellant. Dr Lorentz considered it a possibility (Blue 135M, 138U) but formed no firm opinion that what was involved was a cavernoma.

iii. For the Respondent Dr Kendall did not think there was any evidence of a cavernoma and while Dr Stening, the Respondent's treating neurosurgeon, considered it a distinct plausible explanation for the stroke preferred the thrombotic haemorrhagic stroke hypothesis.

vi. There was no affirmative evidence or scientific evidence to support the view that the Respondent had a cavernoma.

v. The preponderance of the evidence revealed, Dr Kendall only excepted, that if the Respondent had a cavernoma as the aetiological cause of his stroke, then the stroke was not related to his work duties.

vi. Dr Kendall considered that his theory of exertion causing increases in the intracranial blood pressure would act upon an area of weakness, including a cavernoma, to precipitate a stroke.

vii. The common ground between the neurosurgeons was that if the appropriate diagnosis in this case was a cavernoma then the Respondent's stroke was not in any way related to his employment.

i. A thrombotic haemorrhage needs to be distinguished from a thrombotic stroke, the most common form of stroke. It was accepted however that the stroke suffered by the Respondent here was not of that kind.

ii. Professor Stoodley categorised this category as a haemorrhagic stroke, being part of the hypertensive category of strokes, caused by a thrombus (Black 20P-21I).

iii. The main proponent of the thrombotic haemorrhage theory was Dr Stening, the Respondent's treating neurosurgeon.

iv. Professor Stoodley accepted that the pathological mechanism described by Dr Stening was a definite plausible theory but one which on the evidence he personally did not prefer. (Black 20E, 37Lff, 38Kff, 39I, 40K-R, 24K-V).

v. Further Dr Matheson, a qualified neurosurgeon for the appellant, gave support for this pathological process, before Dr Stening's views were expressed (at Blue 41Q and referred to in His Honour's judgment at Red 74I). [it seems the distinction is whether the thrombus forms in the brain itself in which case the stroke is categorised as a haemorrhagic stroke, or if the thrombus forms in another part of the body and travels to the brain in which case it is then considered a thrombotic stroke]

The search for evidence of a cavernoma 45 The evidence before the Court extended to a detailed examination of the CT and MRI scans taken at various points in time none of which had revealed any evidence of a cavernoma. In this regard the evidence included a treatment of the complexities involved where the relevant search was for any remnants of calcium which, if found, would support the hypothesis that a cavernoma was the likely cause. 46 It is strictly unnecessary to repeat the evidence given by the medical experts in relation to this area as it is apparent that albeit that the evidence was equivocal, it was clearly open to the trial judge on the question of fact to find as he did, that on balance, the negative recent CT scan indicated that there had been no cavernoma. 47 Ultimately it cannot be said that there was no evidence or no sufficient evidence which could properly base the finding of the trial judge on this important factual issue. The trial judge was entitled to accept the evidence of Dr Stening supporting the thrombotic haemorrhage theory. Dr Stening had given reasons for his view. Whilst he had accepted that one of the two mechanisms had to be a more probable scenario and that the differences in probability were extraordinarily closely balanced, the fact is that Dr Stening was an experienced [and indeed the treating] neurosurgeon and that the trial judge was perfectly entitled to accept his expert opinion in preference to that of Professor Stoodley, whose evidence supported the cavernoma hypothesis. 48 There is no doubt but that the trial judge was faced with a situation where the matter was difficult to call. However his Honour had:

i. the evidence of Dr Kendall that there was no proof that there was a cavernoma,

ii. Professor Stoodley's and Dr Matheson's acceptance that there was no scientific proof that there was no cavernoma.

iii. Dr Stening's opinion that there was probably no cavernoma.

iv. the circumstance that the radiological evidence, including the delayed MRI scans and the delayed CT scan failed to reveal any evidence of it. 49 In those circumstances it was open for His Honour to draw the conclusion on the balance of probabilities, that there was no cavernoma.

Dealing with the second ground of appeal 50 There is no substance in the contention that the trial judge failed to furnish adequate reasons. The two credible explanations for the stroke put forward respectively by Professor Stoodley and by Dr Stening were carefully examined with a detailed discussion of the reasons for dismissing the cavernoma theory and for accepting that put forward by Dr Stening. The corollary of the dismissal of the cavernoma theory was that the thrombotic stroke theory was accepted and the trial judge gave a reason for accepting this, using the following words:

"[A]lthough the negative recent CT scan was described by one of the specialists as being but a small step backwards as far as the diagnosis was concerned I consider that from the point of view of the probability that the law requires, the step backwards is somewhat more significant". 51 The trial judge discharged his obligation to "state generally and briefly the grounds which [had] led him…to conclusions concerning the disputed questions and to list the findings on the principal contested issues." [Hevi Lift (PNG) Ltd v Etherington [2005] NSWCA 42 (at [100]). Clearly the trial judge went further than "an assertion of satisfaction on undifferentiated evidence."

Dealing with grounds of appeal 3, 4 and 5 52 The question raised by these grounds of appeal concerns the proper approach to the application of s 9A to the injury provision in s 4 of the Workers Compensation Act 1987. 53 It is important to bear in mind that the question of whether employment is a substantial contributing factor is one of fact: WorkCover Authority of New South Wales v Walsh [2004] NSWCA 186 per Hodgson JA at 5 [McClellan AJA agreeing]. 54 The decision of this Court in Mercer v Australia and New Zealand Banking Group Ltd [2000] NSWCA 138 concerned a circumstance in which the reasoning given by the trial judge in the following passage was rejected by this Court:

There is no doubt that the applicant received personal injury in the course of her employment within the meaning of s4. However the precise activity she was carrying out viz. picking something up from a table, was a type of activity that could have occurred elsewhere, for example at home, in a department store or while out at dinner with friends. It was not an activity with any employment characteristics about it. The constitutional state of the patella was a substantial contributing factor requiring as it did very little provocation for the dislocation to occur. The mere fact that the applicant did what she did when she did it is not sufficient in itself to make the employment a substantial contributing factor to the injury. In the relativities of things it was more a coincidence than a contribution. 55 The approach taken by the trial judge was held to betray legal error for the reason that the absence of "employment characteristics" in the precise activity that led to the injury was treated in the concluding sentences of the above passage as determinative. 56 The decision in Mercer established the following propositions: i. that section 9A itself casts considerable light upon its own scope, vide: · subsection (2) offers non-exhaustive examples of matters capable of being taken into account for the purposes of determining whether a worker's employment was a substantial contributing factor to an injury. · subsection (3) mentions two matters that are not determinative. · subsection (4) excludes journey claims (s10), recess claims (s11) and claims by trade union representatives (s12). · there may be more than one substantial contributing factor to a single injury. [Section 9A(1) speaks of "a substantial contributing factor" and not "the substantial contributing factor"]. · the word "substantial" qualifies "contributing factor", thereby indicating that it is the strength of the causal linkage that is in question. (at [15] - [17])

ii. that: · the words "employment concerned" in s9A reinforce the view that it is the work activity in which the worker was engaged at the time of injury that is relevant. · the ultimate question is whether that activity or task was a substantial contributing factor to the injury, bearing in mind that the concept of "a substantial contributing factor to an injury" is exegeted in subsections (2) and (3) of s9A. (at [22])

iii. that: · the term "substantial" may have various shades of meaning. Having regard to the context, it may mean 'large or weighty' or 'real or of substance' as distinct from 'ephemeral or nominal'. (at [26])

iv. that: · no error was disclosed in an acceptance by the trial judge in Mercer that the meaning to be adopted was that "substantial" meant "more than minimal, large or great" [it being important to remember that the word is used in a relative sense, and recognising that other causative factors may be present]. · Section 9A does not require that the employment must be "the" substantial contributing cause, nor does it attempt to exclude predisposition or susceptibility to a particular condition (at [27]) 57 In relation to the holding in Mercer that the requirement that the employment be a contributing factor to the "injury" is not equivalent to the expression "arising out of the employment", Mason P said:

"It is not easy to apply a causation requirement to a provision which continues to define "injury" as including injury arising in the course of employment. However, work has to be found for all of the words used, unless this proves an impossible task. Section 9A(3)(a) does not preclude this, because it goes no further than deeming employment not to be a substantial contributing factor to an injury "merely because" the injury arose in the course of the worker's employment etc." (at [32]) 58 Mason P (at [37]) made the following observations in connection with approach taken in Mercer to the question of what is "substantial":

It may be thought that this construction of s9A leaves a broad area within which the personal judgment of the individual judge as to what is "substantial" may be determinative. So be it, if the legislation uses this language. In Tillmanns Butcheries Pty Ltd v Australasian Meat Industry Employees Union (1979) 42 FLR 331, Deane J pointed out (at 348): The difficulties and uncertainties which the use of the word ["substantial"] is liable to cause are well illustrated by the guidance given by Viscount Simon in Palser v Grinling [1948] AC 291 at 317 where, after holding that, in the context there under consideration, the meaning of the word was equivalent to "considerable, solid or big", he said: "Applying the work in this sense, it must be left to the discretion of the judge of fact to decide as best he can according to the circumstances of each case….

Returning to the reasons for judgment the subject of this appeal 59 In his reasons for judgment Bishop J expressly accepted Mercer as the definitive exposition as to what constituted a "substantial contributing factor" in the present context. 60 There is nothing in the reasons to suggest that the trial judge failed consistently with Mercer, to regard the essential question in terms of whether or not the employment concerned was, within the meaning of s 9A (1) of the Act, "a substantial contributing factor to the injury" as requiring an examination of the strength of the relevant causal linkage. 61 There is nothing in the reasons to suggest that the trial judge misdirected himself on the test of 'bridging the gap' between a contributing factor and a 'substantial contributing factor'. In the case of a duly proven aggravation or acceleration of a pre-existing condition, a claimant will have travelled some of the distance towards showing the employment to have been 'a substantial contributing factor to the injury'. 62 Counsel for the appellant submitted that for the purposes of s 4B (ii) of the Act:

i. It was enough if the contributing factor was a contribution to the aggravation;

ii. Once that contribution had occurred a 'juristic entity' was established;

iv. Section 9A works upon that injury in the same manner in which it works upon an injury within the meaning of s 4(a) [of the definition of 'injury'];

v. The statutory test is not satisfied if there is a substantial contributing factor to the aggravation;

vi. The statutory test is only satisfied if there has been a substantial contributing factor to a fully blown injury. 63 These submissions are misconceived. They fail to recognise that in the circumstance concerning an integer dealt with by s 4(b) (ii) [such as an aggravation of a disease] the only compensation is for the effect of the aggravation and not for the effect of the original non - aggravated disease. 64 His Honour approached the question of construction upon the basis that the case was put as an acceleration or aggravation or deterioration of a pre-existing atherosclerotic condition in which the substantial contributing factor had to relate to the acceleration or aggravation, and not to the underlying condition. There was no error in this approach. The fact that the work-caused dehydration was sufficient to "tip the balance" and was on the evidence, found to satisfy the requirement that it be shown that the employment concerned was a substantial contributing factor to the injury. 65 The matter was one where s 9A left a broad area within which the personal judgment of the trial judge as to what was 'substantial' was determinative. The issue being one of fact, there were clearly facts proved which formed a reasonable basis for the definite conclusion affirmatively drawn [and of the truth of which the trial judge could reasonably be satisfied] justifying the finding that the employment concerned was a substantial contributing factor to the injury. 66 It follows that the third, fourth and fifth grounds of appeal are rejected as without substance.

Dealing with the sixth ground of appeal 67 There is no substance in the proposition that there was no evidence that the employment concerned caused additional material dehydration: · to an extent causative of the acceleration/aggravation, as well as being · a substantial contributing factor to the dehydration. 68 Evidence to this effect was clearly given by Dr Stening. His evidence was that accepting that the respondent over-indulged in alcohol intake to a substantial degree on the previous night, this would lead to significant dehydration; the respondent would have been somewhat dehydrated even if he had had some fluid prior to going to work; the exertion constituted by the heavy physical work which he was carrying out would have increased his 'insensible loss of fluid' to regulate body heat [through the lungs and through the skin]. 69 Dr Stening's evidence was that:

[A]lso in the normal process of breathing one loses water so [the respondent] was working to a point where he was breathing more rapidly than normal, he would lose a bit more water and I think it is not unreasonable to assume that he was already dehydrated, his blood was already thicker than it should have been and the added exertion of work produced more loss of fluid which presumably wasn't adequately replaced by drinking, caused his blood to come even slightly more thicker and tipped him over the edge. It was the final slight-it was a minor factor which produced a major result. It tipped him over the edge between thrombosing and not thrombosing". [Black 53] 70 His opinion was that one or two hours of work by the respondent would have meant that he lost a reasonable amount of water which if his theory was correct, "tipped him over the edge". 71 Dr Stening gave evidence that:

"I believe that work did contribute to the events as the cerebro- vascular accident did occur whilst he was at work, but I believe that the antecedent events such as the potential for arterial disease, the drinking bout whilst not at work, and the dehydration resulting from this, contributed to a figure which I will approximate at 80% to the events which led to his cerebro- vascular accident and subsequent disability. However… the conditions of his work did contribute, but I would attributed a figure of 20% for the contribution by his work…. 72 As is apparent the field of discourse was particularly difficult for the reason that the factual question involved an assessment of the respective sources of dehydration which could only be proved at the level of opinion of these witnesses by the trial judge. 73 Albeit that Professor Stoodley expressed a view that the percentage of further dehydration caused in the course of the work was much lower, the trial judge was entitled to accept the evidence given by Dr Stening. 74 His Honour found that further dehydration beyond that caused by the alcohol intake, would occur with the physical effort involved in the few hours of work even if the respondent did drink from a bottle of water from time to time. The finding was that the dehydration would have had the effect of increasing the viscosity of the blood. The trial judge specifically accepted the evidence that if the thesis of the thrombotic stroke was correct, then the dehydration due to the physical effort would have tipped the balance. 75 The contention that there was no evidence that any additional work-caused dehydration made a difference to the outcome is also rejected. The evidence given by Dr Stening was to this effect. 76 In the result a minor factor was held to produce a major resulting in a circumstance where the issue comprised a question of fact.

Additional reasons given by Hodgson and Santow JJA 77 I have had the opportunity to read and am in agreement with the additional reasons/observations by Hodgson and Santow JJA.

2. Appellant to pay the respondent's costs of the appeal.

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