Causation, Causation, Causation — Is What's Old New Again Or Are Times A 'Changing'

First presented at the CDL Fall Classic.


"Study the past if you would define the future" - Confucius

Just as Confucius guided us so many centuries ago, similarly, in order to understand the concept of causation in accident benefits context, we must look to the past.

The year is 2008. The case of Monks v. ING Insurance1 had now reached Justices Cronk, Gillese and Watt of the Court of Appeal for Ontario. Justice Cronk writing for the unanimous Court summarized the jurisprudence on causation in accident benefits matters to that date:

[85] Athey v. Leonati2 is the leading Canadian case on causation in tort law. In Athey, Major J. reiterated the following well-established principles:

(1) The general, but not conclusive, test for proof of causation is the "but for" test, which requires a plaintiff to show that his or her injury would not have occurred but for the negligence of the defendant (paragraph 14).

(2) In certain circumstances, where the "but for" test is un-workable, causation may also be established where it is demonstrated that the defendant's negligence "materially contributed" to the occurrence of the tort victim's injury. It is not necessary for the plaintiff to establish that the defendant's negligence was the sole cause of the injury (paragraphs 15 and 17).

(3) Liability will be imposed on a defendant for injuries caused or materially contributed to by his or her negligence. That liability is not reduced by the existence of other nontortious contributing causes (paragraphs 22 and 23).

Although tort law clearly limited the use of the "material contribution" test, the accident benefits jurisprudence continued to use it in many instances as the appropriate test for causation. In Monks, Cronk J.A. stated:

More recently, in Resurfice Corpo. v. Hanke3 ... the Supreme Court of Canada clarified the exception to the "but for" causation test and the circumstances in which the material contribution test may be applied. I do not understand Resurfice to alter the basic causation principles that I have described.

Since 2009, both the Court of Appeal and the Supreme Court of Canada indirectly raised scepticism about the jurisprudence supporting the "material contribution" test as the default test in accident benefits matters.

In Clements (Litigation Guardian of) v. Clements,4 Chief Justice McLachlin stated the following:

The legal issue is whether the usual "but for" test for causation in a negligence action applies, as the Court of Appeal held, or whether a material contribution approach suffices, as the trial judge held. For the reasons that follow, I conclude that a material contribution test was not applicable in this case. I would return the matter to the trial judge to be dealt with on the correct basis of "but for" causation.5

As for the "material contribution" test, the Chief Justice McLachlin observed:

The idea running through the jurisprudence that to apply the material contribution approach it must be "impossible" for the plaintiff to prove that the defendant's...

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