What is the test for determining material contribution and causation in a motor vehicle accident case?

Second, plaintiff’s counsel states that the learned trial judge should have instructed the jury with respect to causation in accordance with the principles in Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458. As the defence acknowledged that the motor vehicle accident was the proximate cause of the plaintiff’s injuries, it was not necessary to instruct the jury with respect to the issue of material contribution and causation with respect to the plaintiff’s damages.