R v Ewanchuk, 1999 SCJ 10 (Major):

[37] The words of Fish J.A. in Saint-Laurent v. Hétu, [1994] R.J.Q. 69 (C.A.), at p. 82, aptly
describe the concern which the trier of fact must bear in mind when evaluating the actions of a complainant who claims to have been under fear, fraud or duress:
“Consent” is . . . stripped of its defining characteristics when it is applied to
the submission, non-resistance, non-objection, or even the apparent agreement, of
a deceived, unconscious or compelled will.

[38] In these instances the law is interested in a complainant’s reasons for choosing to participate in, or ostensibly consent to, the touching in question. In practice, this translates into an examination of the choice the complainant believed she faced. The courts’ concern is whether she freely made up her mind about the conduct in question. The relevant section of the Code is s. 265(3)(b), which states that there is no consent as a matter of law where the complainant believed that she was choosing between permitting herself to be touched sexually or risking being subject to the application of force.

[39] The question is not whether the complainant would have preferred not to engage in the sexual activity, but whether she believed herself to have only two choices: to comply or to be harmed. If a complainant agrees to sexual activity solely because she honestly believes that she will otherwise suffer physical violence, the law deems an absence of consent, and the third component of the actus reus of sexual assault is established. The trier of fact has to find that the complainant did not want to be touched sexually and made her decision to permit or participate in sexual activity as a result of an honestly held fear. The complainant’s fear need not be reasonable, nor must it be communicated to the accused in order for consent to be vitiated. While the plausibility of the alleged fear, and any overt expressions of it, are obviously relevant to assessing the credibility of the complainant’s claim that she consented out of fear, the approach is subjective.