See Here We Go … Again for the first part.
I’ll complete the discussion for now – lawyers are trained to do things in threes – by picking on the British Columbia Court of Appeal and British Columbia trial judges who were only doing their jobs. For the latter, that entails applying what their Court of Appeal has said the law is, even if they think it might not be the law. For the former, that entails applying what the Supreme Court of Canada has said the law is, unless there’s a valid way to duck … sorry distinguish it. (Look up South Side Woodwork v. R.C. Contracting (1989) A.R. 161 (AB QB) for the best explanation why that I know of.)
It is, of course, permitted to distinguish an appellate decision if it can be done validly. Still, claiming that a decision by one’s own court of appeal (or a higher court in the pecking order, as the case may be) is per incuriam may not be the best professional career move for a judge looking to move up the ladder, albeit it has been done – the former, anyway – recently, too. See Smith v. Atlantic Wholesalers Ltd., 2012 NSSC 14. I suppose it’s only ironic that (at least in my view) that Smith is dead wrong – the motion judge misunderstood the point of the Supreme Court of Canada decision he thought is contrary to the NSCA decision he declined to apply. I suppose we have to award kudos to strong advocacy.
In what is currently the BCCA’s penultimate comment about the meaning of Resurfice, that court returned to the meaning of Athey material contribution and its conflation of (equation of is a nicer phrase) the Athey material contribution test with the but-for test. The court wrote in Farrant v. Latkin, 2001 BCCA 336 at paras. 9-11:
The general test for causation, established in Athey v. Leonati, … at paras. 13-17, is the “but for” test: “but for” the accident, would the plaintiff have suffered the disabling pain? In Athey, the Court also stated that a plaintiff need not establish that the defendant’s negligence was the sole cause of the injury. If there are other potential non-tortious causes, such as the plaintiff’s spinal degeneration in this case, the defendant will still be found liable if the plaintiff can prove the accident caused or materially contributed to the disabling pain, beyond the de minimus [sic] range.
In Resurfice Corp. v. Hanke, … the Supreme Court affirmed the “but for” test remains the basic test for determining causation, but developed the concept of “material contribution” in a different manner than that used in Athey, formulating a “material contribution” test as an exception to the “but for” test, a matter that is not relevant to this appeal. The Court replaced the Athey definition of “material contribution” to the plaintiff’s injury with the concept of “a substantial connection” between the injury and the defendant’s conduct. …
Thus, in applying the “but for” test, the trial judge was required to consider not just whether the defendant’s conduct was the sole cause of the plaintiff’s disabling pain, but also whether the plaintiff had established a substantial connection between the accident and that pain, beyond the de minimus [sic] level.
In the BCCA’s defence, the view that that a necessary factual cause – the meaning of but-for – has to be a “substantial connection” between the negligence and the injury seems to be what Resurfice held. It is what Resurfice states at para. 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.
Those interested should look at the complete text of that passage in Snell and decide for themselves whether that part of Snell means what Resurfice seems to assert it means. McLachlin CJ, of course, has the the final say (not the least because the Chief Justice was a member of the Snell panel).
On the other hand, I expect I am not the only person who reads Slaw who remembers reading the exchange between the majority and the minority in Peda v. R  S.C.R. 905, 1969 CanLII 22 regarding the meaning of the Court’s prior decision in Binus v. R  S.C.R. 597, 1967 CanLII 15. The majority, in Peda, disagreed with the minority about the meaning of Binus, notwithstanding that the judge who had written the majority concurring reasons Binus reasons wrote the Peda dissent. Binus had a 5 judge panel and 3-2 split. The groupings agreed on the result, not the analysis. Peda had a 9-judge panel. Each of the majority and minority in Peda had 2 judges from Binus. The fifth had retired – one of the two in the concurring minority. However, one of the 2 in the Peda majority was the third judge in the Binus majority. (Humpty Dumpty was right about this, too, at least for law. The meaning of words is ultimately about power.)
In any event, returning to the present, we have the very recent trial decisions in Fuchser v. Wilson, 2012 BCSC 176 and Piper v. Hassan, 2012 BCSC 189. In each case, the trial judge seems to have held that a prior event which was necessary for the occurrence of the injury – an event offered by the defendant as something which would have at least been a partial defence – was not a but-for cause because its causal contribution was less than de minimis. I’ll repeat: the trial judge held that a but-for cause was not a legal but-for cause because it was a a de minimis cause.
The trial judge wrote in Piper at para. 128:
 I find that the plaintiff has not met his burden of proving on the balance of probabilities that but for the motor vehicle accident, he would not have suffered his current low back pain. I find that the motor vehicle accident did not cause or materially contribute to the symptoms of severe and persistent low back pain experienced by the plaintiff during the 10 months following the snow shoveling incident of January 2007, or to his continuing complaints of mechanical back pain. Any contribution of the motor vehicle accident to the plaintiff’s symptoms after January 12, 2007 did not fall outside the de minimis range. I find that the increase in the plaintiff’s low back pain in January 2007 and his ongoing symptoms of mechanical low back pain were the result of the pre-existing and progressive degenerative changes to the plaintiff’s lumbar spine, rather than the motor vehicle accident of August 31, 2006.
The problem isn’t quite as apparent in Fuscher. There, the trial judge wrote only, at paras. 162-163
 It is, of course, the plaintiff’s burden to prove on a balance of probabilities that the defendants’ negligence caused or materially contributed to the plaintiff’s injuries. 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, 1996 CanLII 183 (SCC),  3 S.C.R. 458 at paras. 13-17.
 The primary test for causation asks: “but for” the defendants’ negligence, would the plaintiff have suffered the injury? This 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”: Resurfice Corp. v. Hanke, 2007 SCC 7 (CanLII), 2007 SCC 7 at paras. 21-23.
Wrapping up our historical adventure, let’s go back to Athey to see what Athey actually wrote at para. 13-17.
 Causation is established where the plaintiff proves to the civil standard on a balance of probabilities that the defendant caused or contributed to the injury: Snell v. Farrell, 1990 CanLII 70 (SCC),  2 S.C.R. 311; McGhee v. National Coal Board,  3 All E.R. 1008 (H.L.).
 The general, but not conclusive, test for causation is the “but for” test, which requires the plaintiff to show that the injury would not have occurred but for the negligence of the defendant: Horsley v. MacLaren, 1971 CanLII 24 (SCC),  S.C.R. 441.
 The “but for” test is unworkable in some circumstances, so the courts have recognized that causation is established where the defendant’s negligence “materially contributed” to the occurrence of the injury: Myers v. Peel County Board of Education; 1981 CanLII 27 (SCC),  2 S.C.R. 21, Bonnington Castings, Ltd. v. Wardlaw,  1 All E.R. 615 (H.L.); McGhee v. National Coal Board, supra. A contributing factor is material if it falls outside the de minimis range: Bonnington Castings, Ltd. v. Wardlaw, supra; see also R. v. Pinske 1988 CanLII 3118 (BC CA), (1988), 30 B.C.L.R. (2d) 114 (B.C.C.A.), aff’d 1989 CanLII 47 (SCC),  2 S.C.R. 979.
 In Snell v. Farrell, supra, this Court recently confirmed that the plaintiff must prove that the defendant’s tortious conduct caused or contributed to the plaintiff’s injury. The causation test is not to be applied too rigidly. Causation need not be determined by scientific precision; as Lord Salmon stated in Alphacell Ltd. v. Woodward,  2 All E.R. 475, at p. 490, and as was quoted by Sopinka J. at p. 328, it is “essentially a practical question of fact which can best be answered by ordinary common sense”. Although the burden of proof remains with the plaintiff, in some circumstances an inference of causation may be drawn from the evidence without positive scientific proof.
 It is not now necessary, nor has it ever been, for the plaintiff to establish that the defendant’s negligence was the sole cause of the injury. There will frequently be a myriad of other background events which were necessary preconditions to the injury occurring. To borrow an example from Professor Fleming (The Law of Torts (8th ed. 1992) at p. 193), a “fire ignited in a wastepaper basket is . . . caused not only by the dropping of a lighted match, but also by the presence of combustible material and oxygen, a failure of the cleaner to empty the basket and so forth”. As long as a defendant is part of the cause of an injury, the defendant is liable, even though his act alone was not enough to create the injury. There is no basis for a reduction of liability because of the existence of other preconditions: defendants remain liable for all injuries caused or contributed to by their negligence.
(In passing, Fleming wrote “every” not “frequently”, but we’ll ignore that, here.)
It seems to me that if the causal “contribution” of some causal act to the plaintiff’s injury is so minor as to be de minimis (trivial) that is a damages question, not an causation of injury question. Athey makes that point clear enough. It’s the “original position” paragraph, para. 32
The essential purpose and most basic principle of tort law is that the plaintiff must be placed in the position he or she would have been in absent the defendant’s negligence (the “original position”). However, the plaintiff is not to be placed in a position better than his or her original one. It is therefore necessary not only to determine the plaintiff’s position after the tort but also to assess what the “original position” would have been. It is the difference between these positions, the “original position” and the “injured position”, which is the plaintiff’s loss. In the cases referred to above, the intervening event was unrelated to the tort and therefore affected the plaintiff’s “original position”. The net loss was therefore not as great as it might have otherwise seemed, so damages were reduced to reflect this.
(“better” is underlined in the original)
If we say that a necessary cause was de minimis cause, we’re saying (somehow) that whatever injury that cause has been found to have caused did not alter the injured person’s “original position” in any legally material way. It did not make the injured person worse off than the person would otherwise have been.
It appears that this point has been recognized recently by the majority in an Alberta Court of Appeal decision: Nattrass v. Weber, 2010 ABCA 64 at para. 64. The majority wrote that, in Athey,
the Supreme Court of Canada placed a de minimis limit on the implication of the tort cause by saying it must at least “materially contribute” to the loss to be part of the legal equation.
It’s the majority’s use of “loss” here, rather than “injury” or “harm” that’s key, since “loss” is usually understood as a synonym for “damages”. In addition, the majority wrote at para. 47:
In Athey, de minimis or “non‑material contribution” is an exception to liability where several causes contribute to the damage. It could be described as a type of de minimis defence or limit on liability.
I’ll wrap-up by restricting myself to some obvious (to me anyway) and not so obvious points. I could go on.
1. Para. 15 in Athey is explicit enough. As written, Athey’s material contribution test is a separate test for the existence of factual causation. Validly (in the stare decisis sense of validly)stating otherwise is open to the Supreme Court of Canada. It isn’t to judges lower on the judicial ladder. Again, look up South Side Woodwork v. R.C. Contracting, 1989) A.R. 161, 1989 CanLII 3384 (AB QB) for the best explanation that I know of why. I figured I wouldn’t end the sentence with a preposition, this time.)
2. In the same vein, the material contributing & de minimis bit in Athey, as written, has nothing to do with the but-for test. If the Supreme Court wants to say it did and does it can, of course. And maybe it did implicitly in Resurfice. But it would have been better, for the sake of “clarification”, had the Court been a bit more explicit.
3. The Supreme Court never explained what it meant by Athey material contribution after Athey and before Resurfice. The Walker Estate material contribution test is not Athey‘s material contribution test. That’s explicitly clear in paras. 87-88 of Walker Estate even if the Court used Athey‘s de minimis threshold to explain what was a sufficient enough causal connection. Anybody here want to argue that a “sufficient condition” means what “necessary condition” means? Particularly when Walker Estate states: “Thus, the question in cases of negligent donor screening should not be whether the CRCS’s conduct was a necessary condition for the plaintiffs’ injuries using the “but-for” test, but whether that conduct was a sufficient condition.”?
4. Did the lower courts ever adequately explain the meaning of Athey material contribution? The Ontario Court of Appeal’s Aristorenas at para. 53 was a good start: “The test is invoked because of logical or structural difficulties in establishing “but for” causation, not because of practical difficulties in establishing that the negligent act was a part of the causal chain.” Beyond that? I’ll quote Professor Ken Cooper-Stephenson because it’s safer. “There is nowhere … any sensible description of what is meant by ‘material contribution’.” (Ken Cooper-Stephenson, “Justice in Saskatchewan Robes: The Bayda Tort Legacy” (2007), 70 Sask. L. Rev. 269 at 303).
5. The Ontario Court of Appeal’s position in all of this? Back in 2007, a panel of that court in Barker v. Montfort Hospital, 2007 ONCA 282 at para. 51 wrote that Resurfice “did not alter the state of the law on causation. Rather it confirmed that “the basic test for determining causation remains the ‘but for’ test”. While the Ontario Court of Appeal has referred to Resurfice on occasion, since, no panel has formally signed on to that dictum.
(edited for typos, again, on Feb 12)