What is the law with respect to the burden of proof where there is a sale between relatives for valuable consideration?

Counsel were agreed that the law with respect to the burden of proof where there is a sale between relatives for valuable consideration is that stated by Duff J. in Koop v. Smith (1915), 1915 CanLII 26 (SCC), 51 S.C.R. 554 at p. 558 and 559: I do not think the proposition put thus absolutely is part of the English law or of the law of British Columbia; but I think it is a maxim of prudence based upon experience that in such cases a tribunal of fact may properly act upon that when suspicion touching the reality or the bona fides of a transaction between near relatives arises from the circumstances in which the transaction took place then the fact of relationship itself is sufficient to put the burden of explanation upon the parties interested and that, in such a case, the testimony of the parties must be scrutinized with care and suspicion; and it is very seldom that such evidence can safely be acted upon as in itself sufficient. . . . I may add that I think it doubtful whether the Ontario decisions when properly read really do lay it down as a rule of law that the fact of relationship is sufficient in itself to shift the burden of establishing the burden of proof in the strict sense. 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 loquitur which the tribunal of fact may and will generally treat as a sufficient primâ 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.