Although evidence of prior bad acts is generally barred by Penal Code section 1101, subdivision (a), section 1108, subdivision (a), provides an exception to this rule and states in pertinent part: "In a criminal action in which the defendant is accused of a sexual offense, evidence of the defendant's commission of another sexual offense or offenses is not made inadmissible by Section 1101 if the evidence is not inadmissible pursuant to Section 352." "Sexual offense," for purposes of section 1108, is defined in part as any conduct proscribed by Penal Code section 261which includes "an act of sexual intercourse accomplished with a person not the spouse of the perpetrator . . . where a person is at the time unconscious of the nature of the act, and this is known to the accused. As used in this paragraph, 'unconscious of the nature of the act' means incapable of resisting because the victim . . . was unconscious or asleep." (Pen. Code, 261, subd. (a)(4)(A).) As the trial court concluded, the charged crime here, rape of a sleeping person, fits within the statutory definition of "sexual offense." Section 1108, subdivision (d)(1)(C), also defines "sexual offense" as "contact, without consent, between any part of the defendant's body or an object and the genitals or anus of another person." "Consent" is defined as "positive cooperation in act or attitude pursuant to an exercise of free will. The person must act freely and voluntarily and have knowledge of the nature of the act or transaction involved." (Pen.Code, 261.6.)