So lets take this a bit further.....
If the guy had been drinking too (a fair assumption) then HIS cogniscence of consent will also be impaired. Therefore he cannot be guilty of rape, only of defective judgement. Unless, that is, SHE can prove that he intended to get her drunk in order to have his wicked way with her. Then it would be up to the defence to prove that she was aware of this, and used her drunken state as an excuse to abrogate responsibility.
Its a bit of a mine-field, innit?
Therefore any conviction for rape of an intoxicated female is bound to be an unsound verdict. I rest my case.

P.S. Have some madiera, m'dear?