What is the defence’s position on liability in a motor vehicle accident?

The defence concedes that it is not excused from liability “merely because other causal factors for which they are not responsible also helped to produce the harm” where it is found the defendants’ negligence is a cause of the harm. If the injuries sustained in the accident caused or contributed to the injury, the defendants are fully liable for the damages that flow: Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458 at paras. 19 and 41.

The onus is on the plaintiff to establish that the wrongdoer was the “cause in fact” of the damage and a “proximate cause” of the damage. Those concepts have been summarized in Brewster v. Li, 2013 BCSC 774 at paras. 77-83:

In cases of negligence, the plaintiff must establish: (1) that the defendant was the "cause in fact" of the damage suffered and (2) that the defendant was a "proximate cause" of the damage, "in other words, that the damage was not too remote from the factual cause. ... The remoteness inquiry assumes that but for the defendant's wrongful act, the plaintiff's loss would not have occurred, but places legal limits on the defendant's liability" (Hussack v. Chilliwack School District No. 33, 2011 BCCA 258 at para. 54, 19 B.C.L.R. (5th) 257).