It goes without saying that surreptitiously adding a soporific chemical to someone's drink is a violent felony assault, with or without a sexual act involved. Anyone doing such a thing should spend a considerable amount of time in prison. If sex is involved it is rape.
I've never attended a fraternity party, or the kind of party you describe. If a woman is unconscious due to voluntary intoxication, a sexual act could be considered rape, it would be up to her. If she initiates sex while conscious and passes out during sex, I would not consider it a prosecutable offense (that is my opinion, I don't know what the law says).
The men I knew in my younger days, myself included, would have disapproved of sex with an unconscious woman. I don't know if they would have applied the term "rape," but we would be unlikely to associate with someone who would do that. We knew it was wrong. I don't know if the law considered it a prosecutable offense. Since it was not something that any of us would do, I never really thought about it. I never knew of anyone who had sex with an unconscious woman.
I don't know what percent of women enjoy waking up to sex. I only had that experience once. We woke up in the middle of the night and started having sex. There was no advance consent. We were half asleep.
In the morning she asked me, "Did we have sex last night?" I answered, "Yes, we did."
"That was fun," she said. "I wanted to be sure I wasn't dreaming."
It happened within the context of a relationship, my former wife - Linda, in my story. You'd have to be sleeping together in the first place for it to happen that way.
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I don't know the circumstances under which the convicted rapists were prosecuted. Most of them claimed to be in for murder, but I had access to their records. One actually did commit murder. He killed her boyfriend and raped her. He was a pathetic case. He would sometimes cry when he was deprived of something he thought he should have. He was featured on a TV crime show and he was proud of it.
He died in prison and no one claimed his body. He had a state funeral, no friends or relatives attended.
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Not everyone in a position of authority should be. That judge is an example. There is no excuse for his decision. A judge needs to exercise better judgement than he did.
Around here, it seems that adults are prosecuted for sex with minors, and receive substantial prison sentences. It is usually reported on the local TV news. This is a small, fairly conservative community. The population of the entire county is 80,000, most of it is rural. The size and type of community might make a difference.
I think you are more familiar with the cases that were not prosecuted and I am more familiar with those that were. I am familiar with at least two women who were victims but didn't pursue legal remedies. In both cases, they were hitchhiking.