A panel of the ONCA deserves a PAULI Award for its frolic of law on proof of factual causation in Sacks v. Ross, 2017 ONCA 773 (CanLII), <http://canlii.ca/t/h6hsc>.
Why PAULI?: Because the famous physicist Wolgang Pauli once said about a theory in a physics paper: “”Das ist nicht nur nicht richtig; es ist nicht einmal falsch!” (That’s not just not right; it is not even wrong!) https://rationalwiki.org/wiki/Not_even_wrong
Why PAULI? It’s the closest analogy I could think of to the Darwin Awards: the idea being that the decision will not have descendants – i.e., will not be a precedent – so it has, in that sense, killed itself without progeny by eliminating itself from the legal equivalent of the gene pool.
The explanation for the award should tell you my view of the merits of the panel’s analysis of factual causation law principles.
Some readers will know that wrote a comment on that decision. It was available elsewhere on the web for a time. I have deleted it, for now. It will eventually reappear here, within a week or so, perhaps with some additions.
In the meantime, if you really really really need that commentary in the meantime, email me.
In the meantime, those of you who have to read and consider the merits of the Sacks assertions should keep in mind these three points:
1. In January 2017 the ONCA in Surujdeo v Melady, 2017 ONCA 41 clearly, expressly, specifically, etc., dealt with the issue the Sacks panel decided, AND that earlier panel came to the opposite conclusion. (Take a look at the name of the president of the Surujdeo panel.) The judges on that panel had before them, considered, and approved the analysis of the law as set out by and applied by the trial judge in Sacks. The discussion starts at . The discussion isn’t obiter. The issue of what and how to instruct the jury on factual causation in negligence, what the questions to the jury were to be, was the issue in Surujdeo. Surujdeo is a medical malpractice action with multiple defendants tried with a jury. (The plaintiffs succeeded at trial. The appeal was dismissed.) Nonetheless, it isn’t mentioned at all in Sacks even though Sacks cites Surujdeo as authority on a separate issue. This means we have the procedural issue of whether it was open to the panel to validly undertake the analysis in the manner that it did, regardless of what the proper decision was.
2. In Benhaim v. St‑Germain,  2 SCR 352, 2016 SCC 48, a decision which the Sacks doesn’t mention at all, McLachlin CJC, speaking for a unanimous court – there was dissent on a different issue – wrote
“ 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.”
That comment goes right to the issue of the merits of the panel’s analysis of the law governing proof of factual causation, including the questions and instructions to be given a jury.
3. The seeming claim by the Sacks panel that, essentially, medical malpractice claims with multiple wrongdoers are somehow different in principle, not just more factually complex, requiring not just a more careful analysis but somehow a different analysis in principle than other less complex cases, medical negligence and otherwise. That claim includes this assertion.
“ However, it is worth observing that the Supreme Court has never considered cases beyond the simple.”
I think there’s room to disagree on that claim but decide for yourself. Let’s start, and stop, here, with Benhaim v. St‑Germain and Ediger v. Johnston,  2 S.C.R. 98, 2013 SCC 18 on the medical malpractice side. For other types of case, let’s use Bow Valley Husky (Bermuda) Ltd. v. Saint John Shipbuilding Ltd.,  3 SCR 1210, 1997 CanLII 307 (SCC).
When I last checked, Ontario, like Quebec and BC, was still part of Canada, both geographically and politically.
I realize I’ve yet to say what it is the panel asserted that is so wrong.
If you’re wondering what it is the Sacks panel actually said, and you need to know, it involves the meaning of the but-for test for factual causation in negligence, the proper form of the jury question(s) on factual causation, and what words to use to tell the jury about the meaning of but-for causation. The panel wrote in 
 There are three general issues:
1. Did the trial proceed on a correct understanding of causation in negligence cases?
2. Were the jury questions and the jury instructions on causation legally correct?
3. Did any legal error in the jury questions or the jury instructions deprive the appellants of a fair trial?
Beyond that? Read the decision. I’m trying to maintain some standards, here, for now.
I did write never say never.
I now return to my currently scheduled life.
With the end approaching of what would have been, once upon a time, the “long vacation” and litigators gearing up for the fall court season, it’s time for a fashion tip reminder.
The reminder is that is is no longer the law in common law Canada that, somehow, the but-for test is to be applied differently in civil cases where expert evidence is adduced on the issue of factual causation, even in those places where it was once fashionable to assert it was; even in those places in common law Canada where some seem to think it is still in fashion to assert it is.
As a result of the Supreme Court of Canada decision in Ediger v. Johnston, 2013 SCC 18 (released today), the unique to British Columbia Moore v. Castlegar gloss on Snell v. Farrell is as dead as the parrot in the classic Monty Python sketch.
The BCCA had affirmed that rule in its decision: Ediger v. Johnston, 2011 BCCA 253 at para. 84
 This court confirmed in Moore v. Castlegar& District Hospital (1998), 49 B.C.L.R. (3d) 100, [1998 CanLII 4906] (C.A.) that “where both parties have led expert evidence on the issues of causation, it is not open to this court to apply the ‘common sense’ reasoning urged in Snell”(para. 11).
The SCC’s response at para. 36
 The Court of Appeal’s reasons also suggest that it understood the trial judge to have improperly relied on Snell v. Farrell,  2 S.C.R 311, in order to draw an “inference of causation” (paras. 83-85). Snell stands for the proposition that the plaintiff in medical malpractice cases — as in any other case — assumes the burden of proving causation on a balance of the probabilities (ibid., at pp. 329-30). Sopinka J. observed that this standard of proof does not require scientific certainty (ibid., at p. 328); Clements, at para. 9. The trier of fact may, upon weighing the evidence, draw an inference against a defendant who does not introduce sufficient evidence contrary to that which supports the plaintiff’s theory of causation. In determining whether the defendant has introduced sufficient evidence, the trier of fact should take into account the relative position of each party to adduce evidence (Snell, at p. 330).
I wrote about this issue in more detail earlier, here.
For those who want to know what happened in the appeal: the SCC allowed the plaintiff’s appeal, restored the trial judge’s decision that the defendant was liable, and returned the case to the BCCA to deal with the parties’ damages appeals which the BCCA hadn’t considered since it dismissed the action.
On the merits issues, I think the SCC’s decision is the correct. All one needs to do is read the head-note to understand why.
Added on April 6, 2013
While the central issue in the case was but-for factual causation, there’s nothing in the reasons that should be taken to add to, subtract from, or in any other sense modify anything the Court said in Clements.
The issue is the assessment of the portion of the plaintiff’s future damages where the plaintiff has a relevant pre-existing condition caused by a non-tortious event. What if the evidence is equally balanced pro and con as to what might happen in the future: the future meaning the period after the trial. Since the plaintiff has the onus of proof, does this mean that the plaintiff’s action fails in relation to the claims for which the evidence is equally balanced?