Source: https://davidcheifetz.ca/2013/10/25/something-is-fishy-here-bc-sockeye-ontario-carp/
Timestamp: 2019-04-25 00:59:53+00:00

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[41.2 ] If it was necessary to have both the accidents and the pre-existing back condition for the herniation to occur, then causation is proven, since the herniation would not have occurred but for the accidents. Even if the accidents played a minor role, the defendant would be fully liable because the accidents were still a necessary contributing cause.
In passing, para. 17 of Athey isn’t quite right. It’s more than “frequently”. It’s always. The irony (?) oddity (?) of the paragraph is that the “always” point is made explicitly in the complete passage in Fleming, The Law of Torts, from which Athey took the example in para. 17.
 The plaintiff must establish on a balance of probabilities that the defendant’s negligence caused or materially contributed to an injury. The defendant’s negligence need not be the sole cause of the injury so long as it is part of the cause beyond the de minimis range. Causation need not be determined by scientific precision: Athey v. Leonati,  3 S.C.R. 458 at paras. 13-17.
 The plaintiff must establish on a balance of probabilities that the defendants’ negligence caused or materially contributed to an injury. The defendants’ negligence need not be the sole cause of the injury, so long as it is part of the cause beyond the range of de minimis. Causation need not be determined by scientific precision: Athey v. Leonati,  3 S.C.R. 458 at paras. 13-17, and Farrant v. Laktin, 2011 BCCA 336, para. 9.
For what it’s worth, cases like Alexander and Paller are a pain for those of us trying to keep tabs on the current (mis)state – to coin a neologism – because one can’t run a CanLII search using Clements. What you have to do is run a searches for combinations of caus*, Athey, & Resurfice but without Clements while crossing one’s fingers and dancing widdershins around a broken Sherwood goalie stick. Appropriate hockey gear is optional.
[fn 6] See Clements v. Clements, 2012 SCC 32; Farrell v. Snell,  2 S.C.R. 311; Athey v. Leonati,  S.C.R. 458; Resurfice Corp. v. Hanke,  1 S.C.R. 333; Dinham v. Brejkain (2005), 33 C.C.L.I. (4th) 263 (S.C.J.).
If you decide to read the complete text of both the BCSC and ONSC reasons, ask yourself whether the misstatement of the law is relevant to the judge’s conclusion. Those of you who aren’t familiar with Ontario’s … idiosyncrasies … should keep in mind that Strangis is the text of the trial judge’s reasons on a separate issue of whether the alleged injury was sufficiently serious to meet Ontario’s threshold for actionability of injury allegedly sustained in a motor vehicle accident. It’s not the reasons for judgment in the tort action. That action was tried with a jury. What I’m asking you to do, in Strangis, is ask yourself whether, assuming the trial judge explained causation to the jury in the same way as appears in these reasons, that explanation might have affected the jury’s conclusion on damages.
The sentences in paras.  and  of Andrusko contain literally accurate statements of existing propositions of law, before Clements, but that doesn’t mean that each of the statements makes sense.
We have no idea what meaning the judge is ascribing to “materially contributed” with or without the gloss given to “materially contributed” by the BCCA.
That sentence conflates factual causation with the scope of legal responsibility. Also, if it’s understood to be connected to terms in the first sentence, it implies the judge did mean “materially contributed” in a factual causation sense. That implies a belief in degrees of necessity for factual causation.
“Causation need not be determined by scientific precision”.
Yeah, that’s what Snell and Athey said.
If by “causation” the judge meant all aspects of legal causation the statement is correct but incomplete. If the judge meant factual causation, the statement is literally accurate but meaningless unless one knows what the judge meant by “but for” and “suffered”. That takes us to the next sentence.
23 The “but for” test recognizes that compensation for negligent conduct should only be made “where a substantial connection between the injury and the defendant’s conduct” is present. It ensures that a defendant will not be held liable for the plaintiff’s injuries where they “may very well be due to factors unconnected to the defendant and not the fault of anyone”: Snell v. Farrell, at p. 327, per Sopinka J.
Even if one doesn’t bother to go back and read Snell to get the context of the quoted passage, because one takes the position that the SCC is never wrong in its statements about the meaning of any statement in one of its prior cases – well … at least until another panel restates that meaning in a later decision – the use of “compensation” should be a red flag that that passage isn’t focused just on factual causation, rather, is about the on the scope of legal responsibility. “Factual causation” (whatever meaning one gives that phrase”) is merely an aspect of the legal concept of causation.
Did the notion that, somehow, “change of position” is the defining, always necessary, component of factual causation, and, hence, legal causation where factual causation is required underlie what the judge wrote in Andrusko? If it does, that’s a mistake, too. But that’s a mistake repeated in para. 8 of Clements and existed before Clements. As ever, it’s the analytical (not real) problem of relevant multiple sufficient factual causes in a regime which claims that the but-for test is the definition of factual causation. In Andrusko, the trial judge found that the other factor(s) – here the pre-existing conditions: the other suggested independently (of the neligent act, so not part of the causal set of factors that includes the negligent act) sufficient cause – probably wouldn’t have caused the post accident complaints even if the negligent act hadn’t occurred. That means there was a relevant change of position.
Why did I write “relevant change of position”? Because the other causal candidate, if independently sufficient, of itself, was never actionable. There’d still have been no change in position if the other causal candidate was an actionable event. But then there could be legal responsibility notwithstanding the absence of change of position, because, in common law Canada (as a general rule) we don’t allow the defence of “somebody else’s actionable conduct is also a cause”, regardless of whether “also” means, “together” or “independently”.
The continued failure of too many judges, starting at the SCC, to clearly separate, and keep separate, the concepts of factual causation and scope of legal responsibility is a significant part of the explanation for the confusion in causation jurisprudence. But, then, I’ve said that, before, haven’t I? And, I’m not saying anything that’s new.
Addendum: The Snell statement “injuries … [which] may very well be due to factors unconnected to the defendant and not the fault of anyone” tells us why but-for factual causation isn’t enough for legal causation in a regime that requires some level of relevant causal connection between compensable injury and actionable fault of a wrongdoer. So, the mere fact I’m speeding through the intersection when blue ice falling from flying pigs strikes the passenger in a seat in my convertible doesn’t make my speed a but-for cause for legal purposes, even though the incident would not have occurred had a driven at the speed limit: even though, but-for the fact I was speeding, the vehicle wouldn’t have reached the intersection at the required time.
In addition, given the Snell panel’s position that there was no reason to depart from existing causation principle which were then seen to be adequate when properly applied, so that the SCC, on that basis, rejected what’s now understood to have been, in McGhee, a nascent statement of the material contribution to risk principle, we can see, in the statement “injuries … [which] may very well be due to factors unconnected to the defendant and not the fault of anyone”, room for the rationale for material contribution to risk (MC-R) as explained in Clements. In the MC-R scenario seemingly envisaged by Clements, the same evidence produces the conclusions that the injuries may be due to the actionable fault of a person, are necessarily due to the (at least once actionable) fault of another person: put more simply, “may very well be due to factors connected to the defendant, even if that can’t be established on the balance of probability, and are the fault of someone”.
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