What is the burden of giving evidence in a sexual assault case?

In Koop v. Smith (1915), 1915 CanLII 26 (SCC), 51 S.C.R. 554, Duff J. discussed the “burden” that arises in such instances. He said, “It may be that the proper construction of these cases is that the burden of giving evidence and not the burden of the issue is shifted …. I think the true rule is that suspicious circumstances coupled with relationship make a case of res ipsa loquitor which the tribunal of fact may and will generally treat as a sufficient prima facie case, but that it is not strictly in law bound to do so; and that the question of the necessity of corroboration is strictly a question of fact.”