Gummow J said (at 257-9):
Here, the injury to Mrs Hart occurred within an area of foreseeable risk. In the absence of evidence that the breach had no effect or that the injury would have occurred even if Dr Chappel had warned her of the risk of injury to the laryngeal nerve and of the consequent risk of partial or total voice loss, the breach of duty will be taken to have caused the injury.98
In those circumstances the task of Dr Chappel was to demonstrate some good reason for denying to Mrs Hart recovery in respect of injuries which she would not have sustained at his hands but for his failure adequately to advise her. Dr Chappel founds his case upon the circumstance that injuries of the nature which were sustained by his patient may be caused without negligent performance of the procedure. He joins to that consideration three matters. The first is the circumstance that sooner or later (though it does not appear whether this would have been before Mrs Hart's retirement in August 1985 or, indeed, at any particular time) Mrs Hart would have been obliged to submit to the procedure. The second is the finding by the trial judge that at some future time Mrs Hart would in fact have done so, even after being made adequately aware of the risk. The third is that this later operation would have carried the same risk of injury. Thus, it was said to follow that Mrs Hart had lost no "real and valuable chance ... of the risk [of injury] being diminished or avoided". In support of that conclusion, reliance was placed upon passages in Sellars v Adelaide Petroleum NL 99 which deal with lost opportunities or chances to acquire benefits. However, as is emphasised later in these reasons, Mrs Hart did not sue to recover the value of an opportunity or chance lost to her by the act or omission of Dr Chappel.
In this way the submissions for Dr Chappel tended to divert attention from the central issue, namely whether there was adequate reason in logic or policy for refusing to regard the "but for" test as the cause of the injuries sustained by Mrs Hart, by the allurement of further cogitation upon the subject of "loss of a chance".
Once the criterion for assessment of the adequacy of causation has been determined as a matter of law, the question whether the plaintiff has suffered some damage and therefore has a complete cause of action in tort is normally established by evidence which satisfies the civil standard of proof.100 If causation is not established in this way, then the plaintiff will fail and recover nothing.101
The difficulties which this standard of proof may present to plaintiffs in certain types of litigation have attracted attention in recent times. In Snell v Farrell 102, Sopinka J, who gave the judgment of the Supreme Court of Canada, referred with approval to the treatment of the subject by Professor Fleming. That scholar had written103:
"This traditional approach has come increasingly under challenge in dealing with non-traumatic injuries such as man-made diseases linked to dust, deafness, dermatitis, asbestosis, or linked to chemical products like Thalidomide, DES, and Agent Orange. Another group of cases involves medical procedures depriving patients of a chance of survival or cure. It is often difficult to prove medical causation by particularistic' evidence, that is direct, anecdotal, non-statistical evidence from the mouth of witnesses." The result of the application of the traditional criterion of proof may be to deny plaintiffs any recovery in tort. There has been discussion of alternatives to denial of recovery in obedience to the "more probable than not" civil standard of proof. 104 Writing in 1989, Professor Fleming said of these alternatives:105 "One is to lower the conventional standard and accept exposure to the risk of injury instead of actual injury as a compensable event. Another is to limit liability in an amount proportionate to the risk created by each individual agent. Both of these modifications have gained reluctant and by no means universal acceptance by Anglo-American courts." In Snell v Farrell 106 Sopinka J referred to material suggesting that in the United States the loosening of the criteria for recovery in medical malpractice suits had been followed by the withdrawal of some major insurers from the market.107 Subsequently, in Laferriere v Lawson 108, the Supreme Court of Canada held that it had not been proved on the balance of probabilities that the failure in 1971 of the defendant to inform his patient that the growth removed by him was cancerous had caused her death in 1978. The evidence was that the patient's chances of survival would not have been greater had she been informed in 1971 of the diagnosis. The Court also held that the theory of liability for loss of a chance was not to be adopted in such a case.109 The present appeal does not involve any consideration of whether such means should be adopted to assist recovery by plaintiffs in certain cases. 98 Bennett v Minister of Community Welfare (1992) 176 CLR 408 at 420-421. 99 (1994) 179 CLR 332 at 355, 363-364, 368. 100 Sellars v Adelaide Petroleum NL (1994) 179 CLR 332 at 351, 353. 101 Sellars v Adelaide Petroleum NL (1994) 179 CLR 332 at 368. 102 [1990] 2 SCR 311 at 320-321. 103 Fleming, "Probabilistic Causation in Tort Law", Canadian Bar Review, vol 68 (1989) 661, at p 662. 104 Snell v Farrell [1990] 2 SCR 311 at 326-328. See also Scott, "Causation in Medico-Legal Practice: A Doctor's Approach to the Lost Opportunity' Cases", Modern Law Review, vol 55 (1992) 521; Stauch, "Causation, Risk, and Loss of Chance in Medical Negligence", Oxford Journal of Legal Studies, vol 17 (1997) 205, at pp 213-216.
105 Fleming, "Probabilistic Causation in Tort Law", Canadian Bar Review, vol 68 (1989) 661, at p 663. See also Coote, "Chance and the Burden of Proof in Contract and Tort", Australian Law Journal, vol 62 (1988) 761, at p 772.
106 [1990] 2 SCR 311 at 327.
107 cf Esanda Finance Corporation Ltd v Peat Marwick Hungerfords (1997) 188 CLR 241 at 282-283, 302-303.
108 [1991] 1 SCR 541.
109 Laferriere v Lawson [1991] 1 SCR 541 at 605-606; (1991) 78 DLR (4th) 609 at 656-658.
Kirby J said (at 273-4):
8. Shifting the evidentiary onus: One means of alleviating the burden cast by law on a plaintiff to establish a causal relationship between the breach and the damage concerns the evidentiary onus. Australian law has not embraced the theory that the legal onus of proof shifts during a trial .176 Nevertheless, the realistic appreciation of the imprecision and uncertainty of causation in many cases - including those involving alleged medical negligence - has driven courts in this country, as in England, to accept that the evidentiary onus may shift during the hearing. Once a plaintiff demonstrates that a breach of duty has occurred which is closely followed by damage, a prima facie causal connection will have been established. 177 It is then for the defendant to show, by evidence and argument, that the patient should not recover damages. In McGhee v National Coal Board 178, a Scottish appeal, Lord Wilberforce explained why this was so. Although Lord Wilberforce's statement in McGhee has proved controversial in England,179 it has received support in this Court.180 Its principle has also been accepted by international experts such as Professor Giesen. I find Lord Wilberforce's exposition compelling181:
"[T]he question remains whether a pursuer must necessarily fail if, after he has shown a breach of duty, involving an increase of risk of disease, he cannot positively prove that this increase of risk caused or materially contributed to the disease while his employers cannot positively prove the contrary. In this intermediate case there is an appearance of logic in the view that the pursuer, on whom the onus lies, should fail - a logic which dictated the judgments below. The question is whether we should be satisfied, in factual situations like the present, with this logical approach. In my opinion, there are further considerations of importance. First, it is a sound principle that where a person has, by breach of a duty of care, created a risk, and injury occurs within the area of that risk, the loss should be borne by him unless he shows that it had some other cause. Secondly, from the evidential point of view, one may ask, why should a man who is able to show that his employer should have taken certain precautions, because without them there is a risk, or an added risk, of injury or disease, and who in fact sustains exactly that injury or disease, have to assume the burden of proving more: namely, that it was the addition to the risk, caused by the breach of duty, which caused or materially contributed to the injury? In many cases ... this is impossible to prove, just because honest medical opinion cannot segregate the causes of an illness between compound causes. And if one asks which of the parties, the workman or the employers, should suffer from this inherent evidential difficulty, the answer as a matter of policy or justice should be that it is the creator of the risk who, ex hypothesi must be taken to have foreseen the possibility of damage, who should bear its consequences."