From Russell Brown,* “Cause-in-Fact at the Supreme Court of Canada: Developments in Tort Law in 2012-13” (2014), 64 S.C.L.R. (2d) 327 at 331
(* now a Justice of the Alberta Court of Appeal and Honorary Professor of Law at the University of Alberta; Justice of the Court of Queen’s Bench of Alberta at the time of publication)
It is worth making two observations about the drawing of a causal inference. First, there is nothing unorthodox about the proposition that a fact-finder may draw causal inferences, even in the absence of verifying scientific evidence. Inference-drawing is inherent not only in all causal fact-finding, but in all fact finding. Just as one might infer from evidence that an automobile made a screeching noise immediately prior to a collision that the driver saw the obstruction just before striking it, one may also infer (or not infer) that evidence of risk, of harm and of the surrounding circumstances is so arrayed so as to support the drawing of an inference of a causal relationship between the risk and the harm – and all without the reassurance of expert evidence. And, just as the absence of direct evidence that the driver saw the obstruction before hitting it does not preclude an inference that he or she did, the absence of direct evidence verifying a causal link between risk and harm is similarly not determinative. Fact-finders infer, or they do not infer, and they may do so on evidence that bears only indirectly to the proposition being advanced.
The second observation is that causal inference-drawing is not presented in Snell as some form of alternative or watered-down version of the but for test. If all fact-finding is necessarily inferential, then fact-finding to the but for standard is also inferential. So long as the inference is drawn on a balance of probabilities, causal inference is no alternative to the but for test, but is an instantiation of it. It is how the but for test is to be applied – and not merely in some cases, but in all cases.
 Russell Brown, “The Possibility of ‘Inference Causation’: Inferring Cause-in-Fact and the Nature of Legal Fact-Finding” (2010) 55 McGill L.J. 1, at 30-35 [Brown, “Inference Causation”].
 This was the criticism of Lewis Klar, in Tort Law, 3d ed. (Toronto: Thomson Carswell, 2003) at 403: “[w]hile [inference-drawing] may produce a pragmatic solution to a plaintiff’s dilemma in difficult causation cases, it does depart from the traditional “but for” test, and the balance of probability standard.” This statement does not appear in subsequent editions of Professor Klar’s book.
In Simmons v. Yeager Properties Inc., 2014 BCCA 201 (released on May 20, 2014 so on the BCCA website soon after that) Lowry JA ( A. MacKenzie JA and Goepel JA concurring) wrote:
 … The default framework for causation was described in Clements v. Clements, 2012 SCC 32, as follows:
 The test for showing causation is the “but for” test. The plaintiff must show on a balance of probabilities that “but for” the defendant’s negligent act, the injury would not have occurred. Inherent in the phrase “but for” is the requirement that the defendant’s negligence was necessary to bring about the injury ― in other words that the injury would not have occurred without the defendant’s negligence. This is a factual inquiry. If the plaintiff does not establish this on a balance of probabilities, having regard to all the evidence, her action against the defendant fails.
In Ediger v Johnston, 2013 SCC 18,  2 SCR 98, the unanimous (albeit “only” 7 member panel) agreed, in reasons written jointly by Rothstein and Moldaver JJ:
 This Court recently summarized the legal test for causation in Clements v. Clements, 2012 SCC 32,  2 S.C.R. 181. Causation is assessed using the “but for” test (Clements, at paras. 8 and 13; Resurfice Corp. v. Hanke, 2007 SCC 7,  1 S.C.R. 333, at paras. 21-22). That is, the plaintiff must show on a balance of probabilities that “but for” the defendant’s negligent act, the injury would not have occurred (Clements, at para. 8). “Inherent in the phrase ‘but for’ is the requirement that the defendant’s negligence was necessary to bring about the injury — in other words that the injury would not have occurred without the defendant’s negligence” (para. 8 (emphasis deleted)).
Even if the point in Ediger has been slow to make it this far west, for whatever reason, there’s now Simmons v. Yeager.
[Link updated to CanLII link – 15 Dec 2014]
The trial judge wrote in
Skrepnek v Krochak, 2014 ABQB 358
 Sopinka J. for the Supreme Court in Snell held that factual uncertainty in that case did not automatically defeat the claim but that a “robust and pragmatic approach to the facts” could enable an inference to be drawn even though medical or scientific expertise could not arrive at a definitive conclusion: Snell at para 22. He continued at para 32, stating that “[w]hether an inference is or is not drawn is a matter of weighing the evidence”. This does not negate, however, the “but for” test. It still applies but can be satisfied by the drawing of a causal inference to a balance of probabilities from the circumstances in which risk arose and harm materialized: Clements v Clements, 2012 SCC 32 at para 8,  2 SCR 181. See also Brown J. (as he then was), “Cause-in-Fact at the Supreme Court of Canada: Developments in Tort Law in 2012-2013” (2014) 64 SCLR (2d) 327 at 337.
[Emphasis in bold added].
Your assignment, if you chose to read the case, and comment, here, is to decide whether the trial judge identified “the circumstances” other than (1) “the risk” and (2) the fact that the “harm materialized” which made this case one in which “the circumstances,” other than the fact of the risk and that it materialized, together with the facts that there was a risk of harm and that it materialized – that the plaintiff was injured from that risk – were sufficient to support an inference made on the balance of probability that the negligence was a necessary cause of the injury.
and the “not quite” might result in some lawyer, or even some judge, who ought to, but doesn’t, know better concluding that the “not quite” means that the result of the trial is wrong in law.
I’ll outline, in subsequent postings, why, assuming the evidence was as outlined in the Briante v. Vancouver Island Health Authority, 2014 BCSC 1511 reasons, the case could not have succeeded under any other causation analysis that is now correct, or might arguably be, available, under current Canadian tort law; indeed, that allowing it to succeed would have been contrary to what the Supreme Court of Canada held, in Clements v. Clements, 2012 SCC 32,  2 SCR 181, at paras 7-8 is part of the foundational principles upon which Canadian tort law is based:
 On its own, proof by an injured plaintiff that a defendant was negligent does not make that defendant liable for the loss. The plaintiff must also establish that the defendant’s negligence (breach of the standard of care) caused the injury. That link is causation.
 Recovery in negligence presupposes a relationship between the plaintiff and defendant based on the existence of a duty of care — a defendant who is at fault and a plaintiff who has been injured by that fault. If the defendant breaches this duty and thereby causes injury to the plaintiff, the law “corrects” the deficiency in the relationship by requiring the defendant to compensate the plaintiff for the injury suffered. This basis for recovery, sometimes referred to as “corrective justice”, assigns liability when the plaintiff and defendant are linked in a correlative relationship of doer and sufferer of the same harm: E. J. Weinrib, The Idea of Private Law (1995), at p. 156.
(Emphasis in original.)