R v JA – 2011 SCC 28 (McLachlin):

[36] Section 273.1(2)(b) provides that no consent is obtained if “the complainant is incapable of consenting to the activity”. Parliament was concerned that sexual acts might be perpetrated on persons who do not have the mental capacity to give meaningful consent. This might be because of mental impairment. It also might arise from unconsciousness: see R. v. Esau, [1997] 2 S.C.R. 777; R. v. Humphrey (2001), 143 O.A.C. 151, at para. 56, per Charron J.A. (as she then was). It follows that Parliament intended consent to mean the conscious consent of an operating mind.