Sexual assault
new-south-wales
The crime of rape has been abolished, but what you describe might be sexual assault under s61I of the Cimes Act 1900:
Any person who has sexual intercourse with another person without the consent of the other person and who knows that the other person does not consent to the sexual intercourse is liable to imprisonment for 14 years.
From s61HA
"sexual intercourse" means--
(a) the penetration to any extent of the genitalia or anus of a person by--
(i) any part of the body of another person, or
(ii) any object manipulated by another person, or
(b) the introduction of any part of the genitalia of a person into the mouth of another person, or
(c) the application of the mouth or tongue to the female genitalia, or
(d) the continuation of sexual intercourse as defined in paragraph (a), (b) or (c).
So penetration by a strap on (or anything else) clearly meets 61HA(a)(ii).
There are circumstances in s61HJ where there cannot be consent, relevently:
(1) A person does not consent to a sexual activity if--
(c) the person is so affected by alcohol or another drug as to be incapable of consenting to the sexual activity, or
You describe her as "under the influence", which doesn't sound like "so affected by alcohol or another drug as to be incapable of consenting", particularly where it does not seem to be disputed that she consented to a different type of sexual activity.
Which brings us to s61HI:
(5) A person who consents to a particular sexual activity is not, by reason only of that fact, to be taken to consent to any other sexual activity.
As described, she did not agree to be penetrated by a strap on so she has not given consent.
And s61HK deals with knowledge:
(1) A person (the
"accused person" ) is taken to know that another person does not consent to a sexual activity if--
(a) the accused person actually knows the other person does not consent to the sexual activity, or
(b) the accused person is reckless as to whether the other person consents to the sexual activity, or
(c) any belief that the accused person has, or may have, that the other person consents to the sexual activity is not reasonable in the circumstances.
(2) Without limiting subsection (1)(c), a belief that the other person consents to sexual activity is not reasonable if the accused person did not, within a reasonable time before or at the time of the sexual activity, say or do anything to find out whether the other person consents to the sexual activity.
...
(5) For the purposes of making any finding under this section, the trier of fact--
(a) must consider all the circumstances of the case, including what, if anything, the accused person said or did, and
(b) must not consider any self-induced intoxication of the accused person.
As described, it appears that the accused has possibly been reckless but, in any event, there is no evidence that they "within a reasonable time before or at the time of the sexual activity, say or do anything to find out whether the other person consents to the sexual activity", which means any belief they had that there was consent was not reasonable under 61HK(1)(c).
This assumes that the facts stated in the second paragraph are proven - that's always tricky. Assuming that they are, a conviction is a near certainty. From the Criminal Trials Bench Book suggested jury instruction:
A person who consents to a particular sexual activity is not, by reason only of that fact, to be taken to consent to any other sexual activity. There is evidence the complainant may have consented to [describe relevant sexual activity]. If you decide [she/he] may have consented to that activity, it does not follow that for that reason only [she/he] consented to the act of intercourse alleged by the Crown. [Summarise the evidence and relevant arguments of the parties.]]
Gender
The discussion on gender does not appear to be relevant to the particular case, although it might be relevant in others. In particular, one cannot give consent if one is mistaken about the nature of the sexual activity (s61HJ(1)(i)) or if there was fraudulent inducement (s61HJ(1)(k)).
There has been no case law in NSW regarding whether a mistake about gender identity or sexual orientation would be captured by these provisions or, if they were, this mistake would have to have been induced by the accused. Certainly, under s61HJ(1)(k) they would, but under s61HJ(1)(i) it is not so clear.
In the example you give, the accused was male, held themselves out to be male, and was identified by others as male - apart from your statement in the title, there is no suggestion that they lied about being assigned a different sex at birth or that it even came up. Similarly, the victim holding herself out to be female and identifying as "straight" doesn't mean that she can't consent to sex with any male irrespective of that male's history - or any woman for that matter. There is no "fraudulent inducement"; if she had consented to the strap on (which she didn't), there's no reason to believe that that consent would not have been genuine and valid.