Is consent valid in the context of sexual assault?

LaForest J. in Norberg v. Wynrib, supra at 250, found: [I]n certain situations, principles of public policy will negate the legal effectiveness of consent in the context of sexual assault. In particular, in certain circumstances, consent will be considered legally ineffective if it can be shown that there was such a disparity in the relative positions of the parties that the weaker party was not in a position to choose freely.