Appeal - Claim that workplace stress arising from performance of duties was cause of stroke - Process by which learned Deputy President found that worker's stroke resulted from work related stress questioned - Whether over period of time the workplace stress aggravated, accelerated or exacerbated atherosclerotic process such that stroke occurred earlier than might have done without the contribution of the stress - Whether question of law - Detailed examination of various cases disclosing difference of opinion as to scope of appeal on question of law - Analysis of judgments of appeal courts - Existing dispute resolution process unique - Parliament's intention on creation of appeal process - Objects of Act - Medical evidence considered - There was evidence to support ultimate finding made by learned Deputy President - Found no error of law - Appeal dismissed - S 2(1)(f), s 2(2), s 84, s 85, s 86(1), s 92 Workers Rehabilitation and Compensation Act 1986.

Azzopardi v Tasman UEB Industries Limited (1985) 4 NSWLR 139

Turnbull v New South Wales Medical Board [1976] 2 NSWLR 281

Chamberlain v R [1984] HCA 7; (1983) 153 CLR 521

Pashalis v WorkCover [1994] SASC 5143; (1994) 63 SASR 71

Brown v Allen [1953] USSC 52; 344 US 443, 540 (1953)

Edwards v Noble [1971] HCA 54; (1971) 125 CLR 296

Coal and Allied Operations Pty Ltd v Australian Industrial Relations Commission [2000] HCA 47; (2000) 74 ALJR 1348

Warren v Coombes [1979] HCA 9; (1979) 142 CLR 531

Liftronic Pty Ltd v Unver [2001] HCA 24

Da Costa v The Queen [1968] HCA 51; (1968) 118 CLR 186

Collector of Customs v Agfa-Gevaert Ltd [1996] HCA 36; (1996) 186 CLR 389

Collector of Customs v Pozzolanic Enterprises Ltd (1993) 43 FCR 280

Rohrlach v Christianos (1980) 26 SASR 161

Pham v Workers Rehabilitation and Compensation Corporation and Wingfield Heat Treaters (1995) 181 LSJS 241

Hope v The Council of The City of Bathurst [1980] HCA 16; (1980) 144 CLR 1

Australian Broadcasting Tribunal v Bond and Others [1990] HCA 33; (1990) 170 CLR 321

Churchill v Badenochs Transport Ltd and Devine (1971) 1 SASR 63

Builders Licensing Board v Sperway Constructions (Syd) Pty Ltd [1976] HCA 62; (1976) 135 CLR 616

Treleaven v WorkCover Corporation/MMI Workers Compensation (SA) Ltd (Ridge Park Nursing Home) JD59/1998

WorkCover/MMI Workers Compensation (SA) (Ballestrin Concrete Construction Pty Ltd) v Gianfranco Giocondo Zanini JD125/1999

Grantham v Broken Hill Proprietary Co Ltd [2000] SAWCT 21

WorkCover Corporation/HIH Winterthur Workers Compensation (SA) Ltd (Just Cuts Pty Ltd) [2000] SAWCT 22

Royal Adelaide Hospital v Khammash (2001) SAWCT 22

WorkCover Corporation v Sherriff (Unreported Supreme Court of South Australia (1996) S5831)

Hocking v Bell [1945] HCA 16; (1945) 71 CLR 430, 442, 443

Fernandez v Tubemakers of Australia Ltd (1975) 2 NSWLR 190

Sydney County Council v Furner (1991) 7 NSWCCR 210

EMI (Australia) Ltd v Bes (1970) 2 NSWR 238

Seltsam Pty Ltd v McGuiness; James Hardie and Coy Pty Limited v McGuiness (2000) NSWCA 29

McPhee v S Bennett Limited (1935) 52 WN 8 - 9

1 This is an appeal of the South Australia Police Department ("the employer") from the decision of a learned Deputy President wherein he set aside a determination of the employer, which had rejected a claim for compensation made by Mrs June Barber ("the worker") pursuant to the Workers Rehabilitation and Compensation Act 1986 ("the Act") and determined in lieu thereof that the worker had suffered a compensable disability.

2 The worker suffered a stroke at home on the morning of 28 December 1997. In pursuing a claim for compensation pursuant to the Act, she asserted that workplace stress, arising from the performance of her duties with the employer, was the cause of her stroke.

3 In upholding the worker's claim, the learned Deputy President found that the worker was severely stressed from late 1996 to the date of her stroke and that her employment was the source of that stress. Those findings are not challenged in this appeal.

4 What is challenged is the process by which the learned Deputy President found that the worker's stroke resulted from work related stress.

5 The nature of the stroke suffered by the worker comprised of a thromboembolic occlusion of the left middle cerebral artery. It resulted from an embolus arising from the thrombos detaching from atheroscleratic plaque lined at the origin at the left internal carotid artery.

6 The worker had an adverse family history of atheroscleratic vascular disease. She was a smoker and she had a history of raised serum cholesterol. All of these are recognised risk factors for atherosclerosis and each could explain the fact of the worker's stroke.

7 The issue before the learned Deputy President was whether, notwithstanding the fact that these other factors undoubtedly had a significant role to play in the worker's stroke, workplace stress could also be said to have had a causal link with it.

8 In support of her case that such a causal connection could be established, the worker, through her counsel, put forward two hypotheses. The first was that chronic stress accelerated vascular disease in the carotid artery and that this, in combination with her genetic prepositions and her smoking had caused the stroke. The second was that her stress had impacted upon her insulin resistance and that the high insulin levels that followed facilitated weight gain and that this increased the likelihood of vascular disease.

9 In respect of the first of these arguments, the worker relied upon evidence from Dr Hallpike a neurologist. In arguing the second hypothesis the worker relied upon the evidence of Dr Gale, a physician specialising in allergies.

10 The employer called expert evidence before the learned Deputy President that expressed contrary opinions to those just described. In relation to Dr Hallpike's hypothesis, the employer relied upon the evidence of Professor Craig Anderson, a professor of geriatric medicine and clinical epidemiology. In Professor Anderson's opinion the key factors of the worker's stroke were her cigarette smoking, her genetics, and her above average cholesterol level and impaired glucose intolerance. Whilst Professor Anderson conceded the possibility of a link between the worker's stress and her stroke he was of the opinion that the link in this case was most unlikely.

11 In dealing with Dr Gale's hypothesis the employer relied upon the evidence of Dr Harding, an endocrinologist and Professor Anderson.

12 Dr Harding suggested that the hypothesis of insulation resistance as an independent risk factor in the development of stress was not widely embraced by those with relevant medical expertise. He accepted that chronic stress might worsen the state of insulation resistance but noted that in this case, the worker demonstrated to have insulation resistance 14 months after the stroke at a time when she was under no particular state of stress. He therefore questioned how it could be said that there was a relationship between work related stress and the worker's insulation resistance.

13 The employer contended that its medical experts should have been preferred. It says that the contrary medical opinions were demonstrably unreliable. It contended that underpinning Dr Hallpike's hypothesis of the relationship between work related stress and the stroke was an assertion that the worker suffered from high vascular reactivity and that the evidence placed before the learned Deputy President did not establish that that condition existed.

14 In attacking the second hypothesis, the employer contended that underpinning Dr Gale's opinion was an exacerbated insulation resistance and it submitted again, that there was no evidence placed before the learned Deputy President, to establish that that in fact was present at the time of the worker's stroke.

15 The worker's counsel submitted that whatever view we may have of the evidence that was placed before the learned Deputy President, the issues that were agitated before us on appeal, did not comprise of a question of law. He contended that there was evidence in the form of medical opinions from Dr Hallpike and Dr Gale that there was a causal link, a contributing link between the worker's stress and her stroke. He submitted that the learned Deputy President accepted their opinions, that it was open for him to do so, and that being so, no error of law had been established.

16 In the course of their submissions, both counsel took us to the decision of the NSW Court of Appeal in Azzopardi v Tasman UEB Industries Limited (1985) 4 NSWLR 139. The employer's counsel took us to the judgment of Kirby P (as he then was) at 150 - 151 and in particular to the following passages:-

" ...even where the application of the set of rules to a particular set of circumstances will involve questions of fact and degree, if it can be shown that the decision-maker has misunderstood or misapplied the law in some relevant particular, the decision can be upset as being erroneous in point of law...The stages of their classification are (1) fact-finding; (2) rule-stating; (3) rule application. The most typical error of law, attracting the appeal court's corrective jurisdiction occurs at the `rule stating' stage.... However, it may also occur in the finding of facts if the court or tribunal treats as having occurred what in truth is not shown by the evidence to have occurred. Furthermore, it may occur at the third stage in the application of the law to the facts.

The court is limited, relevantly, to points of law. The finding of what have been called the primary facts of a case does not, in itself, expose the trial judge to review on a point of law, unless it can be shown that there is no evidence of a primary fact and that, this being crucial to his decision, the judge's fact finding has involved an error of law. If there is evidence, or if there are available inferences which compete for the judge's acceptance, no error of law occurs simply because the judge prefers one version of the evidence to another or one set of inferences to another.

But where, because of the development of the obligation of reasoned decision-making, the judge,... exposes his reasons and these reasons demonstrate manifest error or illogicality in the reasoning process; rely on facts which are not established by the evidence or indicate such an unexplained perversity as to suggest that an error has taken place in one of the three stages of the process of judicial decision-making, an error in point of law will be established such as will attract the jurisdiction of this Court and warrant its intervention. ... If the reasons given by judges manifest error in fact-finding, rule stating or application of the rule to the facts or lead inescapably to the conclusion that such an error has occurred, that error will amount to a point of law and the beneficial appellate review provided by the legislation will be available.

It should be no part of our system of justice to condone perverse and completely unreasonable decisions. Least of all should it be so where those decisions are made by judges. Their immunity from appellate review in determining the facts does not extend so far as to exclude appeal where gross error, manifest illogicality and unreasoned perversity demand the intervention of this Court."

17 The employer's counsel took us to the judgment of Glass JA and in particular to the following at 155 - 56:-

"It is clear from these extracts that numerous pejorative expressions in common usage possess a single meaning and are interchangeable. To say of a finding that it is perverse, that it is contrary to the overwhelming weight of the evidence, that it is against the evidence and the weight of the evidence, that it ignores the probative force of the evidence, which is all one way, or that no reasonable person could have made it, is to say the same thing in different ways. Upon proof that the finding of a jury is vitiated in this way, it will be set aside because it is wrong in fact. Since the Act does not allow this Court to correct errors of fact, any argument that the finding of a Workers Compensation Commission judge is vitiated in the same way discloses no error of law and will not constitute a valid ground of appeal."

18 What these judgments demonstrate is a legitimate difference of opinion as to the scope of an appeal on a question of law in the context of an appeal concerning a workers compensation case. Indeed judgments from this Tribunal echo that difference. In view of that and in view of the fact that the outcome of this appeal might turn upon our view of the scope of the Full Tribunal's powers on appeal we think it appropriate to examine this issue in some detail.

19 This appeal is brought pursuant to s 86(1) of the Act that provides that "An appeal lies on a question of law". Simple as the words "question of law" may seem the nature and scope of the appeal process that they enable an appeal court or tribunal to undertake has been the subject of much debate and disagreement.

20 The problem of identifying the powers and duties of an appeal court or tribunal is not limited to appeals of this type. As will become apparent they extend to all forms of appeal.

21 It is generally agreed that there are 6 basic types of appeal. These were identified by Glass JA in Turnbull v New South Wales Medical Board [1976] 2 NSWLR 281 at 297 - 98 as follows:-

"Graded in ascending order, in accordance with the width of the corrective power exercised by the appeal court, they are as follows:

(a) Appeals to supervisory jurisdiction. Only errors going to jurisdiction or denials of natural justice can be ventilated.

(b) Appeals on questions of law only, eg from the Workers' Compensation Commission. Undetermined or wrongly determined issues of fact must be remitted.

(c) Appeals after a trial before judge and jury. The result below will be disturbed if the judge fell into error of law, or if the jury's errors of fact transcend the bounds of reason. But, except for the assessment of damages, issues of fact must be redetermined in a new trial.

(d) Appeals from a judge in the strict sense, eg appeals to the High Court. If the judge has fallen into error of law, or has made a finding of fact which is clearly wrong, the appellate court will substitute its own judgment. Only such judgment can be given as ought to have been given at the original hearing. Later changes in the law are disregarded and additions to the evidence are not allowed: Victorian Stevedoring and General Contracting Co Pty Ltd and Meakes v Dignan.

(e) Appeals from a judge by way of rehearing, eg appeals under s 75A of the Supreme Court Act, 1970. Judicial opinion differs on whether a power to receive fresh evidence is implied: Ex parte Currie; Re Dempsey. Almost invariably, however, it is expressly conferred. If errors of law or wrong findings of fact have occurred below, the appellate court will try the case again on the evidence used in the court below, together with such additional evidence as it thinks fit to receive. Since it will decide the appeal in the light of the circumstances which then exist, changes in the law will be regarded: Ex parte Currie; Re Dempsey; Edwards v Noble.

(f) Appeals involving a hearing de novo, eg appeals from a Court of Petty Sessions to a Court of Quarter Sessions. All the issues must be retried. The party succeeding below enjoys no advantage, and must, if he can, win the case a second time: Sweeney v Fitzhardinge." (footnotes omitted)

22 For present purposes we can ignore the last of these categories.

23 An analysis of the judgments of appeal courts and tribunals concerning the other categories of appeal just described reveal that successful appeals often involve no more than the substitution of one opinion over another, both of which might fairly be regarded as correct. This is so because in some matters there is no clearly right answer as to the law, or to the facts, or as to the application of the law to the facts. On any of those issues, in an appropriate case, reasonable minds may differ. The decisions of appeal courts are littered with strong dissenting judgments, on what are plainly questions of fact, for example: Chamberlain v R [1984] HCA 7; (1983) 153 CLR 521 and on what are plainly questions of law, for example: Pashalis v WorkCover [1994] SASC 5143; (1994) 63 SASR 71. As a result, sometimes an appeal succeeds for no other reason than the fact that a relevant majority of the ultimate appeal court or tribunal has taken a different view of the facts, or of the law, or a combination of the two, than that which was taken by the court or tribunal below. This fact led Jackson J in the United States Supreme Court in Brown v Allen [1953] USSC 52; 344 US 443, 540 (1953) to observe:-

"There is no doubt that if there were a super-Supreme Court, a substantial proportion of our reversals of state courts would also be reversed. We are not final because we are infallible, but we are infallible only because we are final."

24 In Edwards v Noble [1971] HCA 54; (1971) 125 CLR 296 at 314, Windeyer J said much the same:-

"... it is not enough that the primary judge was `in no better position to decide' than a judge on appeal. The question is always should his decision be upset? One sentence from the article by Professor Payne to which I have referred puts the problem:

`If we say that the trial judge was wrong and the House of Lords right on an issue of this sort, it is doubtful whether we are saying more than that the House of Lords differed from the trial judge and that there is no appeal from the House of Lords' ".

25 Although the right to appeal is not fundamental and is a right that can only be conferred by statute it is nonetheless a right that has become ingrained in our legal system. Whilst few would doubt the wisdom of a process that enables a review of a decision that affects individual rights and liabilities, the appeal process does come at a price. It prolongs litigation, adds to cost and delay, engenders uncertainty and it may discourage compromise. A party might be less willing to negotiate in the knowledge that an adverse outcome at trial is not necessarily conclusive.

26 Appeal courts and tribunals have clearly been mindful of both the benefits and disadvantages of the appeal process and of the potential for reasonable minds to differ as to the correct outcome of a case. Doubtless this is a reason why there has been much disagreement over the years as to the scope of a particular species of appeal.

27 We will now cite some examples of the different approaches to the various types of appeals that various judges have taken.

28 We commence with so-called appeal limited to jurisdictional error. The majority and minority judgments in Coal and Allied Operations Pty Ltd v Australian Industrial Relations Commission [2000] HCA 47; (2000) 74 ALJR 1348 reflect significant differences of opinion as to the scope of such appeals. Gleeson CJ, Gaudron and Hayne JJ spoke of identifying whether there had been a jurisdictional error by the Full Bench of the Australian Industrial Relations Commission in terms of whether it had misconceived its role, misunderstood the nature of its jurisdiction, failed to apply itself to the question which the relevant statutory provision prescribed or misunderstood the nature of the opinion that it was to form. Having concluded that the Full Bench did none of these they concluded that it had not made a jurisdictional error in allowing an appeal from a single member of the Commission. In concluding that the Full Bench did commit a jurisdictional error, Kirby J, who was in dissent, seemed to ascribe to the view that if the wrong finding was made or if the result reached was mistaken, a jurisdictional error could be taken to have occurred. Because that is how he viewed the decision of the Full Bench of the Commission he concluded that the Full Federal Court was right to find that the Full Bench had made a jurisdictional error.

29 Similar differences have arisen in respect of so called appeals by way of rehearing. Kirby P traces these in Azzopardi (supra).

30 A comparison of the judgments of Barwick CJ and Windeyer J in Edwards v Noble (supra) and those of Gibbs ACJ, Stephen, Jacobs Murphy and Aickin JJ in Warren v Coombes and Another [1979] HCA 9; (1979) 142 CLR 531 amply demonstrates these differences. Because they highlight some of the issues that we have to deal with some of what was said there bears repeating.

31 In Edwards v Noble Barwick CJ said at 306 - 307:-

"The relevant question here, as I have said, is whether the appellate court, as a matter of judicial restraint, ought to reverse the finding of fact.

In the present case no particular attention is paid to this aspect of the appeal in the reasons for judgment delivered by members of the Full Court: but Mitchell J after remarking upon the advantage which the trial judge had in observing the witnesses said this:

`But we have a duty to consider whether the inferences from those facts drawn by the learned trial judge were justified.'

In my opinion, as expressed, this was not a correct approach to the question of whether or not the finding of fact of the primary judge ought to be disturbed. The question is not whether those inferences were right but whether the appellate court is convinced that they were wrong".

32 In Warren v Coombes (supra), Gibbs ACJ, Jacobs and Murphy JJ said at 551:-

"... an appellate court is in as good a position as the trial judge to decide on the proper inference to be drawn from the facts which are undisputed or which, having been disputed, are established by the findings of the trial judge. In deciding what is the proper inference to be drawn, the appellate court will give respect and weight to the conclusion of the trial judge, but, once having reached its own conclusion, will not shrink from giving effect to it. These principles, we venture to think, are not only sound in law, but beneficial in their operation".

33 Their Honours then went on to say at 552 - 553:-

"The fact that judges differ often and markedly as to what would in particular circumstances be expected of a reasonable man seems to us in itself to be a reason why no narrow view should be taken of the appellate function. The resolution of these questions by courts of appeal should lead ultimately not to uncertainty but to consistency and predictability, besides being more likely to result in the attainment of justice in individual cases. The interest of the community in the speedy termination of litigation might, no doubt, be an argument in favour of the complete abolition of appeals, although that would be far too high a price to pay merely for finality. However, if the law confers a right of appeal, the appeal should be a reality, not an illusion; if the judges of an appellate court hold the decision of the trial judge to be wrong, they should correct it."

34 As an aside we note that their Honours' prophecy about judges differing in their opinions was fulfilled in this very case. The majority thought that the trial judge had erred in finding that the respondent had not driven his car negligently. The minority comprising of Stephen and Aickin JJ concluded otherwise.

35 Differences of the very same type have similarly emerged in respect of appeals after trial before a judge and jury. In Liftronic Pty Ltd v Unver [2001] HCA 24 a majority of the High Court restored a jury's apportionment of liability arising out of an industrial accident essentially on the ground that it was not open for the Court of Appeal to substitute its own opinion as to what the proper apportionment should be. Kirby J took a very different view of the Court's role on appeal. At par 2 and par 3 of his judgment he said:-

"The Court of Appeal had undoubted jurisdiction and power, in this case, to hear the appeal from the judgment of the District Court based on the jury's verdict. Once its jurisdiction was engaged, it had a duty to determine the appeal in accordance with law. The rule of restraint does not, and could not, amount to an absolute rule forbidding the discharge of appellate functions or requiring that such functions always be exercised in one way. Because of the nature of the appeal to the Court of Appeal, that Court's functions necessarily involved a decision that required, on its part, judgment, evaluation and the weighing of competing arguments. So long as the Court of Appeal has shown itself aware of, and has applied, the correct principles, this Court may not disturb the outcome simply because its members would have reached a different result.

... The provision of appeal carries with it the obligation on the part of the appellate court, within its jurisdiction and powers, to perform its functions in accordance with law. Necessarily, this involves the possibility that, in the particular case, those with the appellate responsibility may conclude that the proper discharge of that responsibility requires an order upholding the appeal. The mere fact that this case was one of apportionment does not eliminate that responsibility." (footnotes omitted)

36 Given these differences it is scarcely surprising that the same type of differences have arisen in respect of so called appeals on questions of law. To some extent these emerge from the respective judgments of Kirby P and Glass JA in Azzopardi. But there are numerous other examples.

37 In Da Costa v The Queen [1968] HCA 51; (1968) 118 CLR 186 at 194, 195, Windeyer J said:-

"The distinction between questions of fact and questions of law, like the different but in some ways similar distinction between mistakes of fact and mistakes of law, has been productive of a multitude of cases and of numerous judicial statements which, especially in the field of taxation, are not all easily reconciled. I need do no more than refer to what was said in New Zealand by Gresson P in Commissioner of Inland Revenue v Walker [1963] NZLR 339 at 353 and in this Court in Commissioner of Taxation v Miller [1946] HCA 23; (1946) 73 CLR 93. The topic has excited learned academic commentary - more so in America than in England or here: see Wilson, `A Note on Fact and Law' (1963), 26 Modern Law Review 609. It is now commonly said that the distinction between matters of fact and of law depends upon, is influenced by, and differs with the circumstances in which the question arises. When the distinction determines whether or not in a particular case an appeal lies, there is room for questioning whether it has in philosophy or logic an essential and abstract and universal character. Scrutton LJ in Currie v Commissioners of Inland Revenue [1921] 2 KB 332 at p 339 - a passage quoted by Jordon CJ in Dennis v Watt (1942) 43 SR (NSW) 32 at p 33 - pointed out that -

`... there has been a very strong tendency, arising from the infirmities of human nature, in a judge to say, if he agrees with the decision ... that the question is one of fact, and if he disagrees ... that it is one of law, in order that he may express his own opinion the opposite way.'

This may engender cynicism or stimulate self examination or merely show that the distinction is not capable of precise formulation. The difficulty is in the notion that every question which arises for lawyers can be called either a question of fact or a question of law."

38 In Collector of Customs v Pozzolanic Enterprises Ltd (1993) 43 FCR 280, the Full Federal Court after discussing many of the relevant authorities attempted to identify some general propositions that disclosed the difference between a question of law and a question of fact. In Collector of Customs v Agfa-Gevaert Ltd [1996] HCA 36; (1996) 186 CLR 389 at 394 the High Court referred to that case and noted that:-

"The distinction between questions of fact and questions of law is a vital distinction in many fields of law. Notwithstanding attempts by many distinguished judges and jurists to formulate tests for finding the line between the two questions, no satisfactory test of universal application has yet been formulated."

39 In workers compensation cases in this State the judgment of King CJ in Rohrlach v Christianos (1980) 26 SASR 161 is sometimes cited as providing the touchstone by which to determine whether a question of law is involved. That case, however, dealt with a very different dispute resolution regime in the context of workers compensation cases than that which presently exists. The Workers Compensation Act 1971 provided for a traditional adversarial approach to such cases. Although it allowed for cases to be dealt with summarily: s 39, any party could insist upon a more formal process: s 40 and thereupon the case would be listed for hearing before a Judge with a right of appeal, described as a re-hearing to the Full Industrial Court: s 45 and thereafter a right to appeal to the Full Supreme Court on a matter of law: s 47. It is also notable that in that case Cox J expressed reservations as to whether a question of law was involved.

40 In Pham v Workers Rehabilitation and Compensation Corporation and Wingfield Heat Treaters (1995) 181 LSJS 241 the Full Supreme Court reversed conclusions reached by a Review Officer and by the Workers Compensation Appeal Tribunal that the worker's alleged continuing psychiatric condition was causally linked to an injury sustained by him in compensable circumstances. In so doing, Mullighan J, with whom Cox J agreed, cited Hope v The Council of The City of Bathurst [1980] HCA 16; (1980) 144 CLR 1 at 7 - 8 and Australian Broadcasting Tribunal v Bond and Others [1990] HCA 33; (1990) 170 CLR 321 at 355 in support of the proposition "Whether an inference can be drawn from proven facts is a question of law": Pham (supra) at 253. He concluded "In my view, the inference could have been drawn and the decision to the contrary was an error of law." In Churchill v Badenochs Transport Ltd and Devine (1971) 1 SASR 63 the Supreme Court held that a misapprehension of evidence vital to the conclusion reached amounted to an error of law.

41 These cases suggest a scope of review on a question of law that transcends into factual findings and the process by which they are found. And yet the judgment of Mason J in Australian Broadcasting Tribunal v Bond (supra) referred to by Mullighan J in Pham contains the following statement at 356:-

"That it is said that `There is no error of law simply in making a wrong finding of fact' Waterford v The Commonwealth [1975] HCA 17; (1975) 132 CLR 473 at pp 481, 483, per Brennan J. Similarly, Menzies J observed in Wrench v District Court; ex parte White (1966) 166 CLR 644 at p 654:

`Even if the reasoning whereby the Court reached its conclusion of fact was demonstrably unsound, this would not amount to an error of law on the face of the record. To establish some faulty (eg illogical) inference of fact would not disclose an error of law.'

Thus, at common law, according to the Australian authorities, want of logic is not synonymous with error of law. So long as there is some basis for an inference - in other words, the particular inference is reasonably open - even if that inference appears to have been drawn as a result of illogical reasoning, there is no place for judicial review because no error of law has taken place."

42 The dispute resolution regimes involved in Churchill v Badenochs Transport Ltd and Devine (supra) and in Pham are both very different to the dispute resolution process under which we now operate.

43 Churchill concerned an appeal to the Full Supreme Court from the decision of a Special Magistrate sitting in the then Local Court on a civil case. The environment there comprised of the traditional adversarial approach to litigation. As to the appeal, it was both on the law and the facts; there was no presumption that the decision of the Local Court was right; and the Supreme Court was bound to re-consider the findings and to form an independent judgment: See: Hannan's Local and District Criminal Courts Practice (second edition) at 122.

44 As for Pham, that was conducted under the dispute resolution process that the Act provided for immediately prior to the existing regime. Upon the lodgement of an application for review the Corporation was obliged to attempt to resolve the issues in dispute by agreement: s 95(6), but failing that, the matter was referred to a Review Officer who was obliged to independently review the disputed decision and to make a fresh determination. That process frequently comprised of a hearing in which oral evidence was given: s 90. The decision of the Review Officer could be appealed to the Workers Compensation Appeal Tribunal: s 97(1), that had extensive powers on appeal, including the power to receive oral evidence: s 97(4e). From there, there was a right to appeal, subject to leave, to the Full Supreme Court: s 100.

45 We could cite countless other examples of cases containing statements about the scope of the duties and powers of an appeal court or tribunal that deal with appeals on questions of law. All that they would demonstrate is divisions in opinion of the type just discussed.

46 What emerges from all of this is that the mere use of the words such as "question of law" is not necessarily determinative of the scope of the relevant powers and duties of the relevant appeal court or tribunal. Whilst it is obviously an important factor, in the end, in our view, the better course is to determine what parliament contemplated that the relevant appeal court or tribunal's role would be. That in turn requires a consideration of the history of the relevant legislation, an analysis of the dispute resolution process of which we are a part and a healthy regard for the objects of the Act that created us. Needless to say we also look to decisions from courts of high authority for guidance. But none of them provide a clear answer and the statements that they contain must be viewed from the context in which they were made and with regard to the legislation that created the right of appeal that they exercised or spoke of. We think that this approach accords with what Mason J (as he then was), with whom Barwick CJ and Stephen J agreed, said in Builders Licensing Board v Sperway Constructions (Syd) Pty Ltd and Another [1976] HCA 62; (1976) 135 CLR 616 at 622, when speaking of appeals by way of re-hearing, namely:-

"Primarily it is a question of elucidating the legislative intent, a question which in the circumstances of this case is not greatly illuminated by the Delphic utterance that the appeal is by way of rehearing."

47 We therefore turn to the Act. We commence by noting that it contains an objects section which we are expressly obliged to have regard to in interpreting the Act: s 2(2). One of the stated objects of the Act is "to reduce litigation and adversarial contests to the greatest possible extent.": s 2(1)(f).

48 In the following discussion about the dispute resolution process that the Act provides we shall, for convenience, make reference to the worker and to the Corporation, but what we say may equally apply to other disputing parties.

49 If the Corporation makes a reviewable decision that a worker disputes, the worker may lodge a notice of dispute with the Registrar of the Tribunal: s 90. The Registrar is then obliged to immediately send copies of the notice to the other parties to the dispute: s 90B. WorkCover is obliged to have a suitable person whom it has nominated to the Registrar available to reconsider the disputed decision in light of the matters set out in the notice of dispute and unless the Registrar agrees to extend the time that reconsideration must be completed within 7 days of receipt of the notice under pain of a fine of up to $5000 for non compliance: s 91.

50 If the reconsideration does not resolve the dispute the Registrar must refer the dispute for conciliation: s 91A. Upon referral each party must disclose to the conciliator the existence of and nature of all relevant evidentiary material in the party's possession, including material that might otherwise be privileged: Treleaven v WorkCover Corporation/MMI Workers Compensation (SA) Ltd (Ridge Park Nursing Home) JD59/1998, and unless the conciliator agrees otherwise, if the other party requests it, the other party must be given access to that material: s 92. The conciliator is obliged to identify the issues in dispute to attempt to narrow the issues in dispute and to explore the possibilities of resolving the dispute by agreement. The conciliator is given wide powers in conducting conciliation including the power to require anyone who might assist the process to attend: s 92B. Evidence of offers made in a conciliation conference can be relied upon in subsequent proceedings in deciding issues of costs.

51 If the dispute remains unresolved it is referred for arbitration or judicial determination: s 92D. There is a general requirement for a pre-hearing conference to take place before the Tribunal proceeds to hear a disputed claim: s 94B. In conducting an arbitration the arbitration officer may take into account recommendations made by the conciliator who conducted the conciliation: s 93A(2).

52 Although a single member usually hears a judicial determination, the President may refer the matter directly to a Full Bench: s 94A. If a judicial determination follows arbitration the evidentiary material used in the arbitration may be used and evidence not relied upon at the arbitration may be excluded: s 94C.

53 There are special provisions about costs. If the dispute concerns a lump sum, and an offer is made at conciliation, unless the worker is awarded at least 10 per cent more at arbitration or judicial determination than that which was offered the worker will not recover the costs of the arbitration or judicial determination, as the case may be: s 93B and s 94C(2)(c). Other than that, at all levels of the Tribunal, apart from appeals to the Full Bench, unless the worker acted unreasonably, frivolously or vexatiously in bringing or in relation to the proceedings the worker will recover party/party costs whatever is the outcome: s 95. On appeal, as a general rule, costs follow the outcome.

54 The Tribunal is not bound by the rules of evidence: s 84, it must act according to equity, good conscience and the substantial merits of the case without regard to technicalities and legal forms: s 85.

55 Although the Full Bench of the Tribunal can state a case to the Full Supreme Court on a question of law: s 86A, there is no right of appeal to the Supreme Court. That Court's jurisdiction can only be invoked through proceedings founded on an alleged excess or want of jurisdiction: s 88I.

56 It can be seen that the existing dispute resolution process is unique and is very different to that which preceded it. It contemplates a degree of expedition in the resolution of disputes. Its clear focus is directed towards conciliation, to the parties themselves finding their own solutions and crafting their own outcomes. It cuts across rights such as privilege, that in other jurisdictions might be regarded as sacrosanct. It evinces an intention for the Tribunal to supervise the progress of a dispute once it has entered the Tribunal.

57 In our opinion parliament has clearly revealed an intention to create a process that is designed to fulfil one of the stated objects of the Act, namely "reduc[ing] litigation and adversarial contests to the greatest possible extent".

58 It is from this premise that the scope of our powers and duties on appeal must be determined.

59 Parliament has seen fit to create the facility of appeal but it has also seen fit not to create the conventional form of review following a hearing, namely an appeal on fact and law, nor has it seen fit to allow the Supreme Court the right to review decisions of the Tribunal in the way in which that Court was permitted under the former regime.

60 If a matter has proceeded to trial, despite the strong and persistent efforts of the Tribunal to facilitate the resolution of the dispute by agreement, through the processes of conciliation, arbitration (if that has occurred) and through a pre-hearing conference conducted by a presidential member, it is likely that the matter is difficult, as to the outcome of which reasonable minds might differ. If the case turns upon a point of law one might have expected the parties or the presidential member conducting the pre-hearing conference to consider using the facility provided for by s 94A(1), that is, direct referral to the Full Bench.

61 We do not think that it was parliament's intention for the Full Bench in exercising its appeal powers to evaluate for itself the evidence and to substitute its own findings for those reached below because it happens to disagree with them. We think that parliament intended the Full Bench to simply identify whether there was any evidence to support the findings made below and if there was, for the matter to be left at that.

62 As to the application of the law to the facts as found, we do not think that parliament intended for the Full Bench to interfere with a decision under appeal simply because it might have reached a different conclusion. Reasonable minds can differ as to a great variety of issues arising under the Act such as, for example, whether a worker was working predominantly as a full-time worker: s 4(5); or was working overtime in a regular and established pattern: s 4(8)(a); or whether the terms of a rehabilitation program or a rehabilitation and return to work plan are reasonable: s 26, and s 28B; whether a disability arises from employment, or whether a worker was at a place of employment or was involved in a sporting or social activity at the time of disability: s 30; whether employment was a substantial cause of an illness or disorder of the mind: s 30A; or whether a disability amounts to an incapacity and what is suitable employment: s 35. Thus, the Full Bench in WorkCover/MMI Workers Compensation (SA) (Ballestrin Concrete Construction Pty Ltd) v Gianfranco Giocondo Zanini JD125/1999 was not prepared to entertain a request for it to evaluate for itself whether overtime would have continued to be worked in accordance with an established pattern. It held that that issue was a question of evaluation and degree that did not involve a question of law. Similarly, the majority in Grantham v Broken Hill Proprietary Co Ltd [2000] SAWCT 21 held that the finding by the trial presidential member that conduct amounted to serious and wilful misconduct was a matter of fact and degree that involves a judgment in respect of which reasonable minds may differ. Having found that the decision under appeal did not result from a misdirection or misapplication of the relevant legal principles they concluded that no question of law arose. Applying the same reasoning the majority in WorkCover Corporation/HIH Winterthur Workers Compensation (SA) Ltd (Just Cuts Pty Ltd) [2000] SAWCT 22 held that a conclusion that a worker was at her place of employment at the time of suffering a disabilty involved a question of evaluation and degree and as such did not enliven the Full Bench's jurisdiction on appeal. So too did the majority in Royal Adelaide Hospital v Khammash [2001] SAWCT 66 in holding that the identification of "kind of employment" for the purposes of s 39(2)(a)(i) did not involve a question of law because the conclusion reached was one that was open. There are countless other examples.

63 We acknowledge that this approach has not been universally embraced. With all respect to those who have expressed contrary views, we do not believe that those contrary views reflect what parliament intended.

64 In our view the history of the relevant legislation, the dispute resolution process that parliament has seen fit to create, and the terms of the Act itself, indicate that parliament envisaged that the trial presidential member alone is charged with the duty of finding the facts and applying the law to the facts as found. We think parliament intended for the Full Bench's role to be limited to determining whether there has been a misunderstanding of

legal principle, or an error as to the proper construction of the Act or of some other legislative enactment. If none of these matters are involved, we think that parliament's intention is for the Full Bench to let the decision made below stand. In other words, if there was some evidence to support the findings made or some basis to conclude that the findings did or did not fall within the relevant statutory provision, that has not been shown to have been misunderstood by the trial presidential member, the Full Bench has no right to interfere with the result.

65 By giving pre-eminence to the findings and conclusions reached at first instance, parliament is making it clear to the parties that if they take a matter to trial, absent an error of law, the decision of the presidential member will be final and that this is a factor that will have to be taken into account in deciding whether or not to make or accept or reject an offer of compromise.

66 In this case, there was evidence to support the ultimate finding that was made by the learned Deputy President. It is true that there was a substantial body of contrary evidence. But the best that can be said is that a different result may have been reached. That being so, we have no right to interfere. The appeal must be dismissed.

67 This is an appeal brought by the South Australia Police Department, against a decision of the learned Deputy President, that a stroke suffered by the respondent worker, Mrs June Barber, on 28 December 1997, arose out of her employment.

68 At the hearing before the learned Deputy President there was no dispute that the worker had suffered a stroke. There was no dispute that she suffered from atherosclerosis, a degenerative disease of the arteries, and that the stroke was a consequence of that degenerative condition. The stroke occurred when a thrombus formed on atheromatous plaque and then detached itself from the wall of the left internal carotid artery. It became "a floating plug", a thromboembolus, (AB vol 3 at 19) which occluded the left middle cerebral artery. This occurred on 28 December 1997 when the worker, then aged 48 years, was resting at home in bed towards the end of a period of two weeks annual leave. It was a severe and extensive stroke which left her with right hemiparesis (weakness of the right arm and leg) and a marked degree of dysphasia (impairment of speech) (Hallpike AB vol 1 at 76).

69 The issue at the judicial determination was whether, over a period of time, stress in the workplace aggravated, accelerated or exacerbated the

atherosclerotic process and hence the progress of carotid artery disease, such that a stroke occurred earlier than it might have done without the contribution of the stress. The worker's case at judicial determination was that there were two avenues by which the work stress was causally related to the stroke. Firstly, "by way of the chronic stress interacting with hypertensive vascular response or vascular pathology" (AB vol 3 at 10) which progressed to stroke, or secondly, "by way of neuro-endocrine response based on the presence of high levels of insulin, hyperinsulinaemia" leading again to the development of vascular disease and subsequent stroke. (AB vol 3 at 10)

70 There was no dispute at the judicial determination that the worker had a stressful occupation. She was employed as a computer help desk officer and co-ordinator whose duties included assisting other employees with computer difficulties. A Statement of Agreed Facts was tendered outlining facts as to the context in which the worker performed her duties between 1995 and 1997, from which the learned Deputy President made findings that "work conditions took a great toll on the worker's reserves of psychological strength" and that "she was severely stressed particularly from late 1996 to the date of her stroke" (Judgment par 8).

71 Certain non-contentious medical reports of the worker's treating General Practitioner, Physician and Rehabilitation Specialists and copies of the hospital notes were tendered at first instance which provided the relevant history, treatment and prognosis. Information of significance contained in that material was that prior to her stroke the worker was a smoker of 20 - 25 cigarettes a day, that she did not have a history of high blood pressure (hypertension) leading up to the stroke, or raised blood pressure when admitted to hospital on the day of the stroke, that the day after her stroke she had mildly raised serum cholesterol of 6.6 mmol.L, and that she had a family history of atherosclerosis with both parents and an aunt all dying of coronary heart disease at age 60 or younger. This information was of significance because there was consensus amongst the medical witnesses called to give evidence that family history of heart attack or stroke in one or both parents, cigarette smoking, raised cholesterol, and hypertension, are among the significant and uncontentious independent risk factors of premature atherosclerosis.

72 Against this background, where there may be more than one condition or state of affairs operating to influence the development of the carotid artery disease which culminated in the stroke, the learned Deputy President was required to determine as a matter of fact whether the disability arose from the employment. A task "to be approached by a common sense evaluation of the chain of events and at all times applying the words of the Act to the medical condition as factually determined". (WorkCover Corporation v Sherriff (Unreported Supreme Court of South Australia S5831)). Lander J also said in Sherriff (supra):-

"It is not, on this legislation, a question whether the employment was a material, proximate, real or an effective cause, but a question as to whether on the facts as found the employment was significant enough to still be able to say that the proven disability whether a disability, secondary disability or disease, arises from that employment."

73 After outlining the respective opinions of the medical experts called to express opinions about the likelihood of a causal link between the worker's acknowledged chronic work stress and the occurrence of the stroke, the learned Deputy President concluded that on the balance of probabilities "the effect of the chronic stress was operative to worsen the carotid arteries disease. That in turn effected the timing and the extent of the stroke suffered by the worker" (Judgment par 135).

74 In reaching this conclusion the learned Deputy President accepted the evidence of Dr Hallpike, a neurologist called by the worker, that her vascular disease which culminated in the stroke was contributed to by her family history of atherosclerosis, her smoking and chronic stress at work which accelerated her condition. The learned Deputy President also accepted evidence of an alternative or cumulative influence upon the worker's carotid artery disease supported by the evidence of Dr Gale, a physician specialising in allergy, who has made a study of the role of insulin in disease. Dr Gale expressed the view that the chronic stress to which she was exposed increased her insulin resistance which, he said, could directly lead to vascular disease. The learned Deputy President rejected the contrary opinions of Dr Hetzel, a cardiologist, whose evidence was that, without a history of hypertension, it was not possible for the stress she experienced at work to contribute to the acceleration or aggravation of her atherosclerotic disease which led to the development of the stroke; Dr Anderson, an epidemiologist, who criticised the relevance and value of certain epidemiological studies relied upon by Dr Hallpike; and Dr Harding, an endocrinologist, who disagreed with the evidence of Dr Gale that it had been established that the worker had insulin resistance.

75 In general terms on appeal, Mr Illingworth, counsel for the appellant, did not take issue with the summary of legal principles which the learned Deputy President stated in respect of causation (Appeal tr 22). Rather, he submitted that the learned Deputy President erred in relying on the evidence of Drs Hallpike and Gale to find a sufficient connection between the work stress and the ultimate stroke. Although each of these witnesses furnished alternative or cumulative scientific bases upon which a causal link between the stress and the ultimate stroke might possibly be found to exist, it was submitted that there was no evidence upon which the learned Deputy President could be satisfied on the balance of probabilities that such a link existed in relation to this particular worker. Or to put it another way, that there was no evidence which elevated the opinion evidence that stress was a possible risk factor for stroke, to evidence, on the facts of this particular case, that it was a probable cause of the stroke.

76 An appeal to this Full Tribunal is limited to a question of law. It is well-accepted that no question of law arises where an appellant is merely attempting to re-argue a question of fact which was decided adversely to it at first instance. If, however, the evidence at first instance, even if accepted over contrary evidence, is incapable in law of supporting a primary finding or an inference, then that raises a question of law. (Rohrlach v Christianos (1981) 26 SASR 161; Azzopardi v Tasman UEB Industries Limited (1985) 4 NSWLR 139); McPhee v S Bennett Limited (1935) 52 WN 8 - 9) However, the distinction is not always easy to make. (Rohrlach (supra); Hocking v Bell [1945] HCA 16; (1945) 71 CLR 430, 442 - 443).

77 In a factual matter such as one involving causation the only principle of law which is likely to arise is whether the materials offered justify an inference of probable connection (Fernandez v Tubemakers of Australia Ltd (1975) 2 NSWLR 190 at 197 per Glass JA).

"So long as there is some basis for an inference - in other words, the particular inference is reasonably open - even if that inference appears to have been drawn as a result of illogical reasoning, there is no place for judicial review because no error of law has taken place" (Australian Broadcasting Tribunal v Bond [1990] HCA 33; (1990) 170 CLR 321 at 356 per Mason CJ).

78 In the context of Mr Illingworth's submissions, the task of this appellate body is to consider the submissions which were advanced, to analyse the decision and the reasons, and to evaluate the evidence relied upon to see whether it justifies an inference of probable connection. (Rohrlach supra 163) If there was evidence upon which the learned Deputy President was permitted to find, on the balance of probabilities, that the stroke was promoted that is, aggravated, accelerated or exacerbated, by the worker's exposure to stress in the course of her employment, then his decision cannot be impugned.

79 As it was the evidence of Drs Hallpike and Gale upon which the learned Deputy President relied, it is only their evidence which is directly relevant to the appellant's submission that there is no evidence to support the learned Deputy President's conclusion.

80 Dr Hallpike's evidence can be summarised as follows; Dr Hallpike furnished three reports and gave oral evidence. His first report dated 22 November 1998 (AB vol 1 at 75) commences with a narration of the clinical information obtained from the hospital notes which underpinned his opinion and that of the other medical experts, he described the stroke, and he assumed the existence of stress in the worker's job. Having acknowledged that "While there is a clinical impression that emotional stress and anxiety are risk factors for the development or expression of atherosclerotic vascular disease, scientific evidence is scanty and conflicting" (AB vol 1 at 77), he turned to scientific papers to ascertain the level of evidence that such a link could exist. He started with reference to a leading text (C P Warlow, Stroke, Blackwell Science 1996, at 203) in which stress is included in a list of possible risk factors for ischaemic stroke. He next referred to two epidemiological studies of which he said:-

"These authors hypothesised that acceleration of the arteriosclerotic process might result from neuroendochrine responses to stress or interaction with hypertension. Or that the atherosclerosis itself might be unaltered, but that stroke might be provoked by an effect on blood viscosity or coagulability" (AB vol 1 at 77).

81 The first study was by Harmsen et al (Risk factors for stroke in middle aged men in Goteborg, Sweden. Stroke 1990; 21: 223 - 229) which investigated a number of cardiovascular risk factors. Psychological stress, defined as a feeling of tension, anxiety and irritability, was one of the risk factors investigated. The author concluded amongst other matters that severe psychological stress was associated with a significant increase in the risk of all types of strokes.

82 The second author, House (House A et al. Life events and difficulties preceding stroke. Journal of Neurology, Neurosurgery and Psychiatry 1990; 53: 1024 - 28) found that high long term threat ratings were a risk factor for stroke whereas there was little effect of short term life events.

83 Dr Hallpike then referred to a study by Everson et al (Interaction of work-place demands and cardiovascular reactivity in progression of carotid atherosclerosis BMJ 1979; 314: 553 - 558) which he said showed a positive correlation between stress induced change in blood pressure and progression of carotid artery atherosclerosis. This he said "appears to provide support for blood pressure mediation of adverse effect of sustained stress on the progression of atherosclerosis" (AB vol 1 at 77).

84 He made reference to a contrary study by Macko (Macko et al. Precipitants of brain infarction. Stroke 1996; 27: 1999 - 2004) which found no significant difference between the incidence of stressful life events in the preceding month in stroke patients and matched non-stroke patient controls. Thus he said "These authors concluded that their findings argued against a relationship between recent psychological stress and acute brain infarction". (AB vol 1 at 77)

85 Having set out that information, Dr Hallpike acknowledged the well-known risk factors for stroke as family history of heart attack or stroke in one or more parents, age, hypertension, diabetes mellitus and cigarette smoking. In addition to those risk factors and on the basis of the studies referred to above, he expressed the view that "there is acceptable scientific evidence that sustained stress is a risk factor for stroke". (AB vol 1 at 78)

86 On considering the worker's employment and with the acknowledgment that the level of the worker's stress at work had not been scientifically evaluated, he assumed from the information provided to him that the worker "was exhibiting noticeable signs of stress in the period before the stroke occurred". On that basis he concluded that work related stress could have contributed to the worker's stroke in the sense of contributing to her premature atherosclerosis along with the somewhat more significant and uncontentious risk factors of the family history and cigarette smoking. (AB vol 1 at 78)

87 This continued to be his view in his subsequent report of 7 August 1999 in which he commented upon a contrary opinion expressed by Dr Hetzel in his report of 19 July 1999. Dr Hetzel examined the epidemiological studies referred to by Dr Hallpike and expressed doubt as to the relevance of the studies to the particular circumstances of the worker. This was for two basic reasons; the first that the Everson study was based on a cohort of male participants and the result he said was not applicable to a premenopausal female with a protective level of oestrogen. Secondly, he said that the studies relied upon the operation of stress upon hypertension. Dr Hetzel referred to the absence of evidence that the worker was indeed hypertensive prior to or at the time of the stroke.

88 In the report of 7 August 1999 Dr Hallpike maintained his earlier opinion based on reliance of the particular scientific studies, and dealt specifically with Dr Hetzel's criticisms. He stated that "there is no reason to believe that the findings wouldn't also apply in women". (AB vol 1 at 79) He said his opinion as to the causal connection was fortified by a further study published in Stroke, (Matthews KA et al, Stress-Induced Pulse Pressure Change Predicts Women's Carotid Atherosclerosis, 1998; 29:1525 - 1530) which reported "that measured thickening (intima-media thickness) of the carotid artery in middle aged women was related to the magnitude of change in pulse pressure during mental stress tasks, independent of age, use of HRT, baseline measures of pulse pressure, smoking status and triglyceride levels". Of this study and that of Everson, Dr Hallpike stated that "the tight protocol conditions in the Everson and the Matthews studies designed to identify stress-induced vascular `responders' - shown to be at greater risk of developing carotid atherosclerosis than `non-responders' - do not appear to equate at all well with casual BP measurements of a routine nature". He therefore interpreted these studies as demonstrating that "absence of documented hypertension in the conventional sense doesn't enable one to conclude that an individual would be a `non-responder' under protocol (or workplace) conditions. It follows that sustained hypertension is not after all a prerequisite for stress-related acceleration of carotid atherosclerosis" (AB vol 1 at 79).

89 In his third report dated 12 September 1999 Dr Hallpike again addressed the issue whether stress can contribute to stroke in the absence of hypertension. He did so by referring again in some detail to the Matthews study and certain other more recent studies. Of the Matthews study, Dr Hallpike said that it tested vascular response levels to a short term mental stress test. Dr Hallpike described that, in response to short term mental stress, the subjects were tested for their vascular response by reference to pulse pressure. Then, over time, measurements were taken of their carotid artery thickness and plotted against their vascular responses. The mathematical characteristics of this plot demonstrated conclusions about causality between pulse pressure and vascular thickness. The underlying question being addressed by the study was whether the vascular stress response was purely physiological and therefore normal and unharmful, or pathophysiological that is, abnormal under some circumstances and causing pathology. The method of testing enabled a conclusion to be reached that IMT (intima-medial thickness of the carotid artery wall) "was related to the magnitude of change in pulse pressure ('vascular reactivity') summed across tasks, independent of age, use of HRT, baseline measures of pulse pressure, smoking, triglyceride levels." (AB vol 1 at 80)

90 Having referred to this study, and other recent studies concerning the intima-media thickness of the carotid artery; (Agewell S et al Negative feelings (discontent) oredict (sic) progress of intima-media thickness of the common carotid artery in treated hypertensive men at high cardiovascular risk. Am J Hypertens 1996; 9: 545 - 550: Matsumoto et al Do Anger and Aggression affect carotid atherosclerosis? Stroke 1993; 24: 983 - 986) and O'Leary DH et al. Carotid-artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults. New England J Med. 1999; 340: 14 - 22), (AB vol 1 p 81). Dr Hallpike concluded that "although the precise pathological significance of the increased intima-media thickness end point used in some of these studies appears to be uncertain, increase in this measurement has now been confirmed as a highly significant risk factor for stroke" and that therefore "the evidence at this stage strongly suggests that presence of hypertension as ordinarily defined - essential hypertension - is not a condition for the development of stress induced intima media thickening of the carotid artery". (AB vol 1 at 81)

91 He therefore concluded in the report of 12 September 1999 that:-

"In summary, there is now a considerable body of epidemiological evidence linking stress with progression of carotid artery disease. While the mechanism isn't clear, vascular pathology is greatest in those who display the largest mental stress-induced pulse pressure changes. This relationship has been found not to be conditional on the presence of hypertension. Evidence of a direct relationship between carotid arterial wall thickness and risk of stroke has just been published." (AB vol 1 at 81)

92 Dr Hallpike enlarged upon this opinion in his oral evidence (AB vol 3 at 15 - 69). He explained that his opinion that there was a link between the worker's stress and her stroke was based on epidemiological evidence that stress is a risk factor for stroke (AB vol 3 at 23). This epidemiological evidence demonstrates that:-

"... irrespective of hypertension people who have high vascular reactivity in mentally stressful situations are more at risk for the development of carotid atheroma as judged by ultrasound scanning than people who are low reactors. So the argument goes. We can't say that stress can be excluded in Mrs Barber's case on the basis that she wasn't known to be hypertensive." (AB vol 3 at 25)

93 Of the studies referred to in his reports he reiterated that the epidemiological studies are dealing with the operation of chronic factors and their influence of the progress of atherosclerosis and that "it's the link between the vascular reactants and the atherosclerosis that really the studies claim to show is a scientific connection". (AB vol 3 at 26)

94 He was specifically asked about the value of epidemiological research as a means of determining risk factors in medicine with particular reference to smoking, in respect of which he commented that the role of smoking as a risk factor for stroke is an expression of epidemiological evidence rather than a molecular explanation, yet the acceptance of such evidence is a matter of judgment and weight. (AB vol 3 at 35). He reiterated the role of stress as being not a major factor, but a factor nevertheless, and in the particular circumstances of the worker's case he reiterated that the stress she experienced at work was one of a number of causal factors in the development of her vascular disease, a factor which he apportioned at 10 per cent (AB vol 3 p 38).

95 In his cross-examination Dr Hallpike agreed that there was no evidence that the worker was hypertensive and thus expressed the view that if work related stress did contribute to her cerebral vascular disease it did not do it through the mechanism of hypertension (AB vol 3 at 50). He was referred to the Everson and Matthews studies and agreed that the relevance of those studies in an individual case would depend on whether the individual had high or low vascular reactivity. In the particular circumstances of the worker he agreed that there is no information to determine whether she was a high or low reactor (AB vol 3 at 51).

96 Dr Hallpike was asked the following important questions in cross-examination:-

"Q. If Mrs Barber had a low vascular reactivity - - -

A. If the tests had been done - if that sort of test had been done, yes, and she was found to be a low reactor - - -

Q. - - - and there was no noted progression of carotid atherosclerotic disease would that exclude her stress as a factor?

A. Because she's not hypertensive, then to the best of my knowledge the mechanism that seems to need to be invoked to be able to express some likelihood of the stress being a risk factor with any reasonable degree of confidence involves making reference to this vascular reactivity approach, and if one were told that she'd been in some study and she'd been in a low - supposing someone from the university was conducting workplace research and she'd been in a study and she'd been a low reactor and one had that information, I think that would diminish the credibility because she was also not hypertensive - of talking about the workplace stress as being a quantifiable element in the production of her stroke.

Q. So, as you said, the Everson study doesn't produce a global principle.

A. No. It's a question of whether you are a reactor or not a reactor, and I think that is so with the other studies.

Q. And the fact that Mrs Barber suffered a stroke as a result of atherosclerotic disease of the carotid artery doesn't allow you to infer that she would have been a high reactor?

97 In the context that the worker's vascular reactivity is not known he also said that the Matthews study is of uncertain significance (AB vol 3 at 61).

98 The final significant passage of his evidence was at 65 when at the end of his cross-examination the following exchange took place:-

"Q. But whether stress played an influencing role in Mrs Barber's stroke is something that you're not really in a position to given (sic) an opinion about.

A. I think I have indicated uncertainty about that.

McCUSKER J: That's the point though, I think - if I could articulate my understanding of Dr Hallpike's position - he is not asserting it as a scientific fact to which dissent should not be available. He is expressing it in this particular case as an opinion on the totality of the material and on the basis that yes, as a fact the thing is a possibility and then in the opinion, in this case - in his judgment in this case - it has [been] a contributory factor. It has been a contribution, albeit a lesser one than other factors. Is that a fair overview of - - -?

A. Yes. I wanted to qualify what I said and that was the way I did it. Thankyou."

99 It was Dr Hallpike's agreement that the worker was not hypertensive prior to or at the time of the stroke, and the unknown status of the worker's vascular reactivity, upon which Mr Illingworth's submissions were concentrated. And it was the passage of evidence quoted in par 96 above to which he directed particular attention. He submitted that the existence of either hypertension or hypersensitivity were fundamental links between the work stress and the occurrence of the stroke, without which there was no evidence upon which the learned Deputy President could draw the inference of causation. Furthermore, Mr Illingworth submitted that the learned Deputy President erred in his approach to this lack of evidence; that he described hypertension and vascular reactivity as mechanisms for a link between stress and stroke, and that he wrongly discounted the lack of evidence of a link by taking the stance that "While it would be preferable to know the mechanism of that link, the mechanism is not one of the requirements to validate the expert's opinion" (Judgment par 16). Mr Illingworth submitted that, without the evidence as to vascular reactivity, a link between stress and stroke could be put no higher than a possible risk; that in the words of Hope J in Sydney County Council v Furner ((1991) 7 NSWCCR 210) "To establish that medical evidence supports a conclusion that the cause could not be excluded as a cause of an injury does not establish, without more, that the particular cause in fact resulted in or caused the injury".

100 In reaching his conclusion the learned Deputy President specifically addressed the significance of the lack of information as to the worker's vascular reactivity status with particular reference to his reliance upon the opinion of Dr Hallpike. This was done in the following manner; His Honour noted that Dr Hallpike's evidence was that of an expert and that his evidence involved an expression of opinion as to the link between stress and stroke in circumstances where that matter has not advanced to the status of an established fact. The learned Deputy President accepted that Dr Hallpike's evidence, in that regard, was supported by epidemiological studies of a link between stress and stroke. (Judgment par 125) The learned Deputy President had earlier accepted that epidemiological evidence, directed to whether a particular factor is capable of causing a particular disease, is admissible evidence of "general causation" which must be weighed in the balance with other factors when determining, whether or not on the balance of probabilities, an inference of causation in a specific case could or should be drawn. (Judgment par 113 - 121) On this issue the learned Deputy President adopted the approach of Spigelman J in Seltsam Pty Ltd v McGuiness; James Hardie and Coy Pty Limited v McGuiness (2000) NSWCA 29.

101 Within the context of the epidemiological evidence of a link between stress and stroke, the learned Deputy President viewed Dr Hallpike's reference to vascular reactivity as an attempt to explain a mechanism not yet known to medical science. His Honour viewed the worker's reactivity status as a matter which cannot be proved by tangible or demonstrable fact. However, he regarded its significance as a disputable point upon which the evidence of experts might differ. He then accepted Dr Hallpike's evidence, to which I have specifically referred, which appears at par 98 above, that in his judgment on the available evidence in this particular case, stress has been a contributory factor.

102 To put it colloquially that was the "bottom line" of Dr Hallpike's evidence. And it was evidence that the witness was qualified to give and upon which the learned Deputy President was entitled to rely in whole or in part. As it transpired, he accepted it as the encapsulation of Dr Hallpike's overall assessment of causation in this particular matter.

103 It is accepted that the inability of medical science to explain the causal connection between a particular act, omission or state of affairs and a specific injury or disease, or the inability of medical science to identify "the biological or pathological mechanisms by which diseases develop" does not necessarily determine "the existence or non-existence of a causal relationship for the purposes of attributing legal responsibility" (Seltsam per Spigelman CJ par 93). In such circumstances "where the aetiology of a disease is uncertain, or subject to significant scientific dispute, the Courts are not thereby disenabled from making decisions as to causation on the balance of probabilities" (Seltsam par 94).

104 In that context Spigelman CJ in Seltsam par 94, quoted Herron CJ in EMI (Australia) Ltd v Bes (1970) 2 NSWR 238 at 242:-

"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 a 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."

105 The relevant medical evidence in this case certainly did not deny the possibility of a connection between stress and stroke. (In addition to Dr Hallpike's evidence set out above see also Dr Hetzel's evidence at 183 - 184 of Appeal Book vol 3.) Therefore the learned Deputy President was entitled to act on "his own intuitive reasoning". In doing so he relied on Dr Hallpike's evidence, together with the undisputed facts. The passage quoted in par 98 above, in the context of the whole of the evidence given by Dr Hallpike, provides the necessary evidentiary foundation for "general causation" and "specific causation" as postulated by Spigelman CJ in Seltsam, or to put it another way, Dr Hallpike's evidence was not limited to issues of general or theoretical consideration contained in the scientific material but provided a sufficient basis for its particular application to the worker, thus enabling the learned Deputy President to draw an inference of causation on the balance of probabilities. In expressing his final opinion, quoted in par 98 above, Dr Hallpike can be assumed to have taken into account matters referred to earlier in his reports and his evidence namely, the accepted stressful work situation, the epidemiological studies to which he referred, the contrary epidemiological studies which he had researched, the contrary opinions expressed by the other medical witnesses, the absence of hypertension at any relevant time, the absence of certainty about the worker's vascular reactivity status and the "clinical impression that emotional stress and anxiety are risk factors for the development or expression of atheroscleroic vascular disease" (AB vol 1 at 77). Criticism of the significance of any of those matters would go to the weight of the evidence and not to the question whether there was evidence at all upon which the learned Deputy President could rely.

106 The other alternative or cumulative basis upon which the learned Deputy President concluded that causation was established was the evidence of Dr Gale that the worker was insulin resistant, a condition which he said was an independent contributor to atherosclerosis.

107 Mr Illingworth submitted that there was no evidence upon which the learned Deputy President could establish such a causal connection on the balance of probabilities. I can deal briefly with this issue. Dr Gale ordered the performance of a two hour glucose and insulin tolerance test on the worker 14 months after her stroke. The test results revealed levels consistent with impaired glucose tolerance and significant hyperinsulinaemia, such conditions being in his view aggravated by stress (AB vol 1 at 100). Dr Gale expressed the view that insulin resistance has a direct role in increased vascular disease and that in this case it was probable that the increased insulin resistance acted upon the worker's vascular system, caused a worsening of her atherosclerosis and contributed to the onset of the stroke.

108 Mr Illingworth submitted that, even accepting the accuracy of the test demonstrating insulin resistance, such test was performed some time after the stroke and that a positive result at that time did not provide evidence of a similar level prior to or at the time of the stroke. Hence it was argued that there was no evidence upon which the learned Deputy President could draw the inference that such condition was in existence prior to the stroke, or that it was aggravated by work stress, or that it contributed, through atherosclerosis, to the occurrence of the stroke.

109 Dr Gale gave specific evidence that, notwithstanding that the test was not undertaken until 14 months following the stroke, it is evidence of an underlying insulin resistance. This evidence was specifically accepted by the learned Deputy President over contrary evidence of Dr Harding. The learned Deputy President was entitled to accept Dr Gale's evidence. That was evidence upon which he could draw an inference of causation. On this aspect too, the appellant fails. There was no error of law and the appeal is therefore dismissed.