Can inferences of causation be drawn in a motor vehicle accident?

In Snell v. Farrell at p. 19 [D.L.R. p. 301], Sopinka J. set out that inferences of causation were necessary in some instances. He stated that: The legal or ultimate burden remains with the plaintiff, but in the absence of evidence to the contrary adduced by the defendant, an inference of causation may be drawn, although positive or scientific proof of causation has not been adduced.