The hallmark of an O. Henry story is its surprise ending.
About 3 years ago, in 2012, in Clements v. Clements,  2 SCR 181, 2012 SCC 32, in reasons by McLachlin C.J., the unanimous 9 member Supreme Court (McLachlin C.J., LeBel, Deschamps, Fish, Abella, Rothstein, Cromwell, Moldaver and Karakatsanis JJ) – agreed: (1) the material contribution test is a material contribution to risk test, not a material contribution to injury (harm) test; (2) the material contribution test should always have been understood as the former and not the latter; and (3) the material contribution to risk test is not based on and does not produce a finding that negligence is a factual cause of injury.
 “But for” causation and liability on the basis of material contribution to risk are two different beasts. “But for” causation is a factual inquiry into what likely happened. The material contribution to risk test removes the requirement of “but for” causation and substitutes proof of material contribution to risk. . . . “material contribution” does not signify a test of causation at all; rather it is a policy-driven rule of law designed to permit plaintiffs to recover in such cases despite their failure to prove causation. …
 While the cases and scholars have sometimes spoken of “material contribution to the injury” instead of “material contribution to risk”, the latter is the more accurate formulation. As will become clearer when we discuss the cases, “material contribution” as a substitute for the usual requirement of “but for” causation only applies where it is impossible to say that a particular defendant’s negligent act in fact caused the injury. It imposes liability not because the evidence establishes that the defendant’s act caused the injury, but because the act contributed to the risk that injury would occur. …
[Citation omitted; text of para. 14 reformatted.]
In Henry v. British Columbia (Attorney General), 2015 SCC 24 – given where this is going, the plaintiff’s surname is apt and ironic – the hearing panel was composed of McLachlin C.J. and LeBel, Abella, Moldaver, Karakatsanis, Wagner and Gascon JJ. As such, the Henry panel had 4 of the 6 judges who decided Clements and were still on the Court: McLachlin C.J., Abella, Moldaver and Karakatsanis JJ. The two who did not sit on the Henry panel were Cromwell and Rothstein JJ.
Accurately stated, the Henry panel had 5 of the Clements judges. The reasons had 4 of the Clements‘ judges. Lebel J., although he sat on the Henry panel, retired before the release of the Henry reasons and took no part in the judgment.
In Henry, Moldaver J. (Abella, Wagner and Gascon JJ. concurring: the majority group had 2 of the judges from Clements) wrote:
 The “but for” causation test may, however, be modified in situations involving multiple alleged wrongdoers. For example, where the claimant alleges that a wrongful conviction was caused in part by the failure of police to provide material information to prosecutors, and in part by the Crown’s failure to disclose, then a showing of “but for” causation will not be necessary. In this scenario, the causation requirement will be satisfied if the claimant can prove that the prosecutorial misconduct materially contributed to the harm suffered: Clements v. Clements, 2012 SCC 32,  2 S.C.R. 181.
[Emphasis added.] The Moldaver J. reasons contain nothing else that explains the use of “materially contributed to the harm”; the meaning of that phrase; or, the suggestion that Clements is authority for the existence of a “materially contributed to the harm” test as a “modification” of the but-for test.
In joint reasons concurring in the result, McLachlin C.J. and Karakatsanis J. (both of whom where on the Clements panel: recall that the Clements reasons are attributed to the Chief Justice) wrote on the causation issue:
[ 118] … As the issue of causation was neither addressed in the decisions below nor argued before us, we prefer to leave any detailed discussion for another day. This said, we are not convinced that the “but for” test proposed by Moldaver J. is appropriate here.
McLachlin C.J. and Karakatsanis J. said nothing about the “materially contributed to the harm suffered” portion of para. 98 of the majority reasons.
I expect there will be more spilled ink. I’m inclined to leave it to others. Maybe there’s some O. Henry in that, too.
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