The judgment of McLachlin C.J. and Karakatsanis, Wagner and Gascon JJ. was delivered by
Wagner J. —
 As I will now explain, Snell and St-Jean held that the ordinary rules of causation must be applied in medical malpractice cases. As prime examples of how the ordinary rules of causation operate in medical liability cases, these decisions are equally relevant in Quebec.
 The majority of the Court of Appeal relied in large part on this passage to justify its conclusion that Snell created a rule of law that requires an adverse inference of causation in certain circumstances. The inference of causation Sopinka J. described in Snell is one that trial judges are permitted to draw even in the absence of positive or scientific proof. It is not one that they are required to draw once certain criteria are established. The decision on whether to draw such an inference is left to the discretion of the trial judge. Despite using permissive language to describe the adverse inference in Snell, the decision of the majority of the Court of Appeal failed to give effect to the permissive, discretionary nature of that inference.
 By overturning the trial judge’s decision on the basis of an error of law, the majority of the Court of Appeal implicitly transformed the permissive inference described by this Court in Snell into one that is compulsory once certain facts are established. The majority’s decision would have the effect of creating a novel legal rule governing presumptions. And yet it is apparent that Sopinka J. was not purporting to create such a rule in Snell. Rather, he was simply describing how the usual fact-finding process works in the medical malpractice context:
It is not strictly accurate to speak of the burden shifting to the defendant when what is meant is that evidence adduced by the plaintiff may result in an inference being drawn adverse to the defendant. Whether an inference is or is not drawn is a matter of weighing evidence. The defendant runs the risk of an adverse inference in the absence of evidence to the contrary. This is sometimes referred to as imposing on the defendant a provisional or tactical burden. . . . In my opinion, this is not a true burden of proof, and use of an additional label to describe what is an ordinary step in the fact-finding process is unwarranted. [Emphasis added; pp. 329-30.].
 In any event, I am of the view that any doubt which might have existed over the appropriate interpretation of Snell in the Quebec civil law context was assuaged by this Court’s decision in St-Jean. As the Court explained at para. 116 of its judgment:
To the extent that such a notion is a separate means of proof with a less stringent standard to satisfy, Snell, supra, and definitely Laferrière, supra, should have put an end to such attempts at circumventing the traditional rules of proof on the balance of probabilities. There may be a misapprehension of what I said in Laferrière, supra, at p. 609: “In some cases, where a fault presents a clear danger and where such a danger materializes, it may be reasonable to presume a causal link, unless there is a demonstration or indication to the contrary”. . . . This is merely a reiteration of the traditional approach on presumptions, and does not create another means of proof in Quebec civil law in the establishment of the causal link. The Court of Appeal correctly interpreted this passage as pertaining to presumptions within the traditional rules of causation. [Emphasis added; emphasis in original deleted.]
 Though the majority of the Court of Appeal was attempting to redress an injustice which it perceived, its decision was inconsistent with these teachings, as it purported to lower the threshold for drawing presumptions of fact. The majority’s view leads to the conclusion that, because of the concern in medical malpractice cases regarding a plaintiff’s inability to produce scientific or direct evidence of causation by reason of a physician’s fault, a trial judge would be required to draw a presumption against a defendant physician even where the presumption could not be said to be serious, precise and concordant. Rather, greatly lowering the threshold, the majority held that a judge is required to draw a presumption where there is “little affirmative evidence” adduced by the plaintiff.
 Additionally, though the holding of the majority of the Court of Appeal seems, at first glance, to be applicable only to a small number of medical malpractice cases, if we were to accept its position, there is no principled reason why its reasoning could not extend to many other professional liability cases where a defendant’s negligence precludes proof of causation with scientific certainty.
 The trial judge did not commit an error of law in applying the rules of evidence. She applied St-Jean, pursuant to which presumptions of causation can be drawn only when they are serious, precise and concordant. She did not think that these criteria were met because she chose to believe Dr. Ferraro, the defendants’ expert, over the plaintiff’s experts. She was not required by law to draw a presumption of fact which was for the defendants to rebut simply because (i) it was impossible to prove causation as a result of the defendants’ fault; and (ii) the plaintiff adduced “some affirmative evidence” that the defendants’ fault was linked to the loss.
 Therefore, in my respectful view, the trial judge committed no error of law in her causation analysis, and the majority of the Court of Appeal should not have intervened on that basis. The trial judge’s finding on causation was thus reviewable solely on the stringent standard of palpable and overriding error.
 Drawing an inference from a general statistic in a particular case is an inherent, and often implicit, part of the fact-finding process. A statistic alone reveals nothing about a particular case. It must be interpreted in light of the whole of the evidence. This interpretation is the role of the trial judge, and it is entitled to considerable deference on appeal. Respectfully, the Court of Appeal in this case failed to show such deference.
 The trial judge in this case acknowledged the statistic that 78 percent of fortuitously discovered cancers are at stage I. She recognized that Mr. Émond’s cancer was fortuitously discovered (para. 119). In considering the evidence as a whole, she declined to infer from those facts that Mr. Émond’s cancer was probably at stage I, as she was entitled to do. By contrast, the majority of the Court of Appeal simply treated the statistic as evidence in itself of a 78 percent probability that Mr. Émond’s cancer was at stage I (paras. 204, 207-8 and 211-12) simply because it was fortuitously discovered. In doing so, the majority usurped the role of the trial judge.
 It was for the trial judge to decide what weight, if any, to give to that statistic in Mr. Émond’s case. She had a reasonable basis for giving it very little. As originally put to Dr. Ferraro, the defence expert, during cross-examination, the statistic related to cancers fortuitously discovered by CT screening, a more precise diagnostic tool. CT screening would be logically expected to reveal a higher proportion of early stage cancers than fortuitous discovery resulting from a mass initially identified on an X-ray, which is why it was the recommended follow-up to Mr. Émond’s November 2005 X-ray in the first place. Moreover, Mr. Émond remained asymptomatic throughout his progression to stage IV cancer: trial court decision, at para. 130. Mr. Émond could easily have had his cancer discovered fortuitously at any stage in its progression. As a result, it was open to the trial judge to find that the general correlation between fortuitous discovery and early stage cancer was a poor basis from which to draw an inference in this case. She committed no palpable and overriding error in disregarding it.
 The same principle of deference applies to the trial judge’s consideration of the average life expectancy of patients diagnosed with stage III or IV lung cancer. According to the plaintiff’s expert, Dr. Langleben, a patient diagnosed with stage III lung cancer generally survives 12 months without treatment, and a patient diagnosed with stage IV lung cancer generally survives 8 months without treatment: trial court decision, at para. 143. In this case, from the time he had stage III cancer, Mr. Émond survived 14 months without treatment (from November 2005 to January 2007), and an additional 17 months with treatment (from February 2007 to June 2008). In Fournier J.A.’s view, these figures ought to have precluded a finding that Mr. Émond’s cancer was already at an advanced stage at the time the defendants negligently failed to diagnose it (paras. 92-93). As with the 78 percent statistic, the experts’ views of the average survival periods for patients with advanced stage lung cancer were available to the trial judge as a basis for inferring that Mr. Émond’s cancer could not have been at an advanced stage in November 2005. But they were not determinative. It was open to her to find that Mr. Émond’s survival for longer than average between November 2005 and June 2008 was a departure from statistics that could be explained by his overall good health (para. 144).
 It could be said that it would have been open to the trial judge to find in favour of the plaintiff, particularly if individual components of the evidence had been examined in isolation. However, the trial judge carefully weighed the evidence as a whole, including both the statistical evidence and the evidence specific to Mr. Émond. Against that backdrop, she considered and evaluated three expert opinions, all of which necessarily involved some speculation. Her causation analysis was based on all of this evidence. She made no palpable and overriding error in finding that the plaintiff had failed to establish causation on a balance of probabilities, and deference to her conclusion is in order.
Appeal heard: April 28, 2016
Judgment rendered: November 10, 2016
|Citation:||Benhaim v. St‑Germain, 2016 SCC 48 (CanLII), <http://canlii.ca/t/gvk2h>, retrieved on 2016-11-11|