Appeals - Standard of Review - Fact-findings
Torts - Causation - Spoliation
Benhaim v. St‑Germain (SCC, 2016)
In this case the Supreme Court of Canada usefully reviews the nature of, and reasons for, the high 'palpable and overriding error' standard applied to review fact-findings of a trial court on appeal or judicial review:
 The standard of review is correctness for questions of law, and palpable and overriding error for findings of fact and inferences of fact: Housen v. Nikolaisen, 2002 SCC 33 (CanLII),  2 S.C.R. 235, at paras. 8, 10 and 19; St-Jean, at paras. 33-36. Causation is a question of fact, and so the trial judge’s finding on causation is owed deference on appeal: St-Jean, at paras. 104-5; Clements v. Clements, 2012 SCC 32 (CanLII),  2 S.C.R. 181, at para. 8; Ediger v. Johnston, 2013 SCC 18 (CanLII),  2 S.C.R. 98, at para. 29.The court then continued to canvass basic principles of causation in the context of medical malpractice, including the situation where a party's inability to prove a fact is due to the negligent or other behaviour of the other party (spoliation):
 It may be useful to recall the many reasons why appellate courts defer to trial courts’ findings of fact, which were described at length in Housen, at paras. 15-18. Deference to factual findings limits the number, length and cost of appeals, which in turn promotes the autonomy and integrity of trial proceedings. Moreover, the law presumes that trial judges and appellate judges are equally capable of justly resolving disputes. Allowing appellate courts free rein to overturn trial courts’ factual findings would duplicate judicial proceedings at great expense, without any concomitant guarantee of more just results. Finally, according deference to a trial judge’s findings of fact reinforces the notion that they are in the best position to make those findings. Trial judges are immersed in the evidence, they hear viva voce testimony, and they are familiar with the case as a whole. Their expertise in weighing large quantities of evidence and making factual findings ought to be respected. These considerations are particularly important in the present case because it involves a large quantity of complex evidence.
 It is equally useful to recall what is meant by “palpable and overriding error”. Stratas J.A. described the deferential standard as follows in South Yukon Forest Corp. v. R., 2012 FCA 165 (CanLII), 4 B.L.R. (5th) 31, at para. 46:
Palpable and overriding error is a highly deferential standard of review . . . . “Palpable” means an error that is obvious. “Overriding” means an error that goes to the very core of the outcome of the case. When arguing palpable and overriding error, it is not enough to pull at leaves and branches and leave the tree standing. The entire tree must fall. Or, as Morissette J.A. put it in J.G. v. Nadeau, 2016 QCCA 167, at para. 77 (CanLII), [translation] “a palpable and overriding error is in the nature not of a needle in a haystack, but of a beam in the eye. And it is impossible to confuse these last two notions.”
 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.
 I will begin by discussing Snell, in which Sopinka J. examined developments in English tort law that purported to reverse the onus of proving causation in some circumstances. Traditionally, the plaintiff in a common law negligence claim had to prove on a balance of probabilities that, but for the defendant’s negligent conduct, the plaintiff would not have been injured. Sopinka J. stated that his task was “to determine whether a departure from well-established principles is necessary for the resolution of this appeal” (p. 320). Sopinka J. concluded that such a departure was not warranted, provided that the traditional principles are not applied in an overly rigid manner (p. 328).
 First, Sopinka J. held that it is not necessary that the plaintiff adduce expert scientific or medical evidence definitively supporting the plaintiff’s theory of causation, as “[c]ausation need not be determined by scientific precision” (p. 328; see also pp. 330-31). This is because the law requires proof of causation only on a balance of probabilities, whereas scientific or medical experts often require a higher degree of certainty before drawing conclusions on causation (p. 330). Simply put, scientific causation and factual causation for legal purposes are two different things. Factual causation for legal purposes is a matter for the trier of fact, not for the expert witnesses, to decide: Laferrière v. Lawson, 1991 CanLII 87 (SCC),  1 S.C.R. 541, at pp. 607-8; see also Sentilles v. Inter-Caribbean Shipping Corp., 361 U.S. 107 (1959), at pp. 109-10.
 Second, in medical malpractice cases, the defendant is often in a better position than the plaintiff to determine the cause of the injury (p. 322). Sopinka J. held that, in such circumstances, the trier of fact may take into account the relative ability of each party to present evidence on a fact in issue:
The legal or ultimate burden remains with the plaintiff, but in the absence of evidence to the contrary adduced by the defendant, an inference of causation may be drawn although positive or scientific proof of causation has not been adduced. If some evidence to the contrary is adduced by the defendant, the trial judge is entitled to take account of Lord Mansfield’s famous precept. [p. 330]This precept, stated by Lord Mansfield in Blatch v. Archer (1774), 1 Cowp. 63, 98 E.R. 969, at p. 970, is that evidence should be “weighed according to the proof which it was in the power of one side to have produced, and in the power of the other to have contradicted” (quoted in Snell, at p. 328).
 An inference of causation is available to trial judges by virtue of the ordinary operation of these principles in the medical malpractice context:
In many malpractice cases, the facts lie particularly within the knowledge of the defendant. In these circumstances, very little affirmative evidence on the part of the plaintiff will justify the drawing of an inference of causation in the absence of evidence to the contrary. 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.
(Snell, at pp. 328-29)
 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.]. The adverse inference of causation described in Snell is permissive precisely because it is a component of the fact-finding process. For the same reason, the question of whether an inference is warranted in a particular case falls within the discretion of the trier of fact, to be determined with reference to all of the evidence. This principle was recently reaffirmed by this Court in Ediger, at para. 36. It was therefore not open to the majority to substitute its own decision to draw an unfavourable inference. Rather, the majority of the Court of Appeal would have been bound to find a palpable and overriding error in the trial judge’s decision not to draw an adverse inference. I return to this point below.
 Snell itself provides an example of the circumstances in which an inference of causation may be drawn. The plaintiff sued the defendant ophthalmologist after she became blind in her right eye following cataract surgery. Before the surgery, the defendant noticed some bleeding when he injected anaesthetic, yet he negligently continued the surgery. The blindness could have been caused by the bleeding or by natural causes. The expert witnesses could not definitively determine the cause. In concluding that the plaintiff had established that the defendant’s negligence caused her blindness, Sopinka J. stated:
The [defendant] was present during the operation and was in a better position to observe what occurred. Furthermore, he was able to interpret from a medical standpoint what he saw. In addition, by continuing the operation which has been found to constitute negligence, he made it impossible for the [plaintiff] or anyone else to detect the bleeding which is alleged to have caused the injury. In these circumstances, it was open to the trial judge to draw the inference that the injury was caused by the retrobulbar bleeding. There was no evidence to rebut this inference. . . . In sum, the Court held in Snell that “the plaintiff in medical malpractice cases — as in any other case — assumes the burden of proving causation on a balance of the probabilities”: Ediger, at para. 36. Causation need not be proven with scientific or medical certainty, however. Instead, courts should take a “robust and pragmatic” approach to the facts, and may draw inferences of causation on the basis of “common sense”: Snell, at p. 330-331; Clements, at paras. 10 and 38. The trier of fact may draw an inference of causation even without “positive or scientific proof”, if the defendant does not lead sufficient evidence to the contrary. If the defendant does adduce evidence to the contrary, then, in weighing that evidence, the trier of fact may take into account the relative ability of each party to produce evidence: Ediger, at para. 36.
. . . it is not essential to have a positive medical opinion to support a finding of causation. Furthermore, it is not speculation but the application of common sense to draw such an inference where, as here, the circumstances, other than a positive medical opinion, permit. [pp. 335-36].