Can a plaintiff argue that pre-existing medical conditions, unrelated to any car accident, be taken into account in the context of a crumbling skull theory?

In arguing Z v. Dominion of Canada, supra, the defendant used the case out of context. The case does not stand for the proposition that when confronted by with two accidents, an arbitrator must decide which insurer is responsible to pay benefits. In the Z case, there weren’t two accidents and two insurers fighting over which one had to pay. The arbitrator was pondering whether pre-existing medical conditions, unrelated to any car accident, were to be taken into account in the context of a crumbling skull theory. This case, I reiterate, confirms the plaintiff’s contention that, in an insurance benefit case, it is no defence to argue that benefits should be reduced in order to reflect an apportionment of causation.