What is the legal test for a defence of automatism?

Whenever a defence of automatism is before the court, there must always be an awareness of the policy concerns described by Mr. Justice Dickson, as he then was, in R v. Rabey (1980) 1980 CanLII 44 (SCC), 54 C.C.C. (2d) 1 at 27: There are undoubtedly policy considerations to be considered. Automatism as a defence is easily feigned. It is said the credibility of our criminal justice system will be severely strained if a person who has committed a violent act is allowed an absolute acquittal on a plea of automatism arising from a psychological blow. The argument is made that the success of the defence depends upon the semantic ability of psychiatrists tracing a narrow path between twin shoals of criminal responsibility and an insanity verdict. Added to these concerns is the in terrorem argument that the flood gates will be raised if psychological blow automatism is recognized in law.