Idea: Password of consent
What if, in order to consent to sex, a woman had to give a man a secret password which he could not know unless she had consented to sex?
This may not be a fool proof way of proving/disproving consent in rape cases; because passwords are not fool proof, there are ways of finding them out, for example, but it certainly might make it harder for men to have sex with women without their consent and also harder for women to make false rape claims.
The passwords would have to be stored in some very secure way; perhaps given to the police or to a lawyer or doctor; to some third party who could then corroborate a rape victim’s testimony in court as to whether or not they had given consent.
Such a system furthermore, would be very difficult to use in long term relationships; a woman would have to keep making up a new password for every time she slept with her partner.
But I do think it could work in situations where a victim is not in any relationship with the person they accuse.