Resurfice Corp v Hanke

Resurfice clarified that the but-for test remains the dominant causation analysis in Canadian negligence law. Material contribution to risk is available only when but-for cannot be applied because of a multi-tortfeasor evidentiary impasse.

Hanke, an ice-resurfacer operator, accidentally filled the gasoline tank with hot water. The water vapour ignited and exploded. He sued the manufacturer alleging design negligence in the placement and labelling of the tanks.

When may a court depart from the but-for test for causation?

But-for applied; trial judge's finding of no causation restored.

Causation is to be established under the but-for test except in the rarest of cases where (a) it is impossible to prove but-for due to factors outside the plaintiff's control, and (b) it is clear the defendant's breach exposed the plaintiff to an unreasonable risk and the plaintiff's injury falls within the ambit of that risk. Material contribution is a substitute for causation only in such cases.

McLachlin CJ rejected an expansive reading of material contribution. The exception is narrow because material contribution dilutes the rigorous link between fault and harm. The case before the Court was an ordinary single-tortfeasor product-liability claim; but-for applied straightforwardly.

Tightened Canadian causation doctrine. Reaffirmed in Clements v Clements (2012), which clarified material contribution applies primarily in multi-tortfeasor cases where the plaintiff cannot say which defendant's negligence caused harm.

Resurfice Corp v Hanke, 2007 SCC 7, [2007] 1 SCR 333.

McLachlin CJ, Bastarache J, Binnie J, LeBel J, Deschamps J, Fish J, Abella J, Charron J, Rothstein J