What is the test for establishing cause or contributory factors in a motor vehicle accident?

Counsel relied on Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458 where Major J. dealt with the “but for test” that requires that the plaintiff only show the injury of which he complained would not have occurred but the defendant’s negligence. Causation is established where the defendant’s negligence materially contributes to the injury occurrence of and a contributing factor is material if it falls outside the minimum range. The defendant admitted liability but his evidence was not credible and proved very little by way of injury.