What is the test for establishing causation in a motor vehicle accident case?

Factual causation is addressed using the “but for” test. The plaintiff must show on a balance of probabilities that, but for the negligence, the damage would not have occurred: Clements v. Clements, 2012 SCC 32. At para. 8, McLachlin C.J.C. made it clear that if the plaintiff falls short of showing that the alleged negligent acts were not necessary to bring about the damage, her case fails: Inherent in the phrase “but for” is the requirement that the defendant’s negligence was necessary to bring about the injury ― in other words that the injury would not have occurred without the defendant’s negligence. This is a factual inquiry. If the plaintiff does not establish this on a balance of probabilities, having regard to all the evidence, her action against the defendant fails.