but it backs up part of his story. As of right now, there is no evidence that even proves that he blacked out. If the prosecution wants to say he got drunk and high, raped homegirl and then left, having ruhypnol in his system gives some credence to his defense that she provided the pills and that he blacked out.

Just like the police collect every little thing that could possibly be used against the suspect, maybe the use it maybe they don't...i'd want every piece of evidence that backs up my story to be accounted for to in case it contradicts a possible prosecution theory/argument.

Maybe the prosecution is gonna argue that he drugged the girl and forced her to drink while he remained sober? Isn't it possible there'd be different degrees of murder if he did it sober vs. in a drug-induced rage?