Anon asked:
At what point, and in what situation, is a person responsible for sex that they have had?
People are always responsible for the consequences that can occur from consensual sex, such as pregnancy and/or STDs.
I believe you are asking about situations other than completely consensual sex (such as sexual activity with an intoxicated person, etc), or else this question makes no sense to me. If that is the case, then what you are actually asking is at what point are people responsible for being raped, and the answer is: never.