R v Ewanchuk, 1999 SCJ 10 (Major):

[25] The actus reus of sexual assault is established by the proof of three elements: (i) touching, (ii) the sexual nature of the contact, and (iii) the absence of consent. The first two of these elements are objective. It is sufficient for the Crown to prove that the accused’s actions were voluntary. The sexual nature of the assault is determined objectively; the Crown need not prove that the accused had any mens rea with respect to the sexual nature of his or her behaviour: see R. v. Litchfield, [1993] 4 S.C.R. 333, and R. v. Chase, [1987] 2 S.C.R. 293.