First off, no, his defense relies on "I'm a good person, it never happened, here are all these women who also say I'm a good person and four witnesses in particular". Second, I forget the particular exchange but he explicitly denied ever being blackout drunk and then refused to answer the clarifying question, so he definitely has been, but honestly: if it suddenly was corroborated by a friend that he has been blackout drunk before, is that really a smoking gun? Or does that even provide a better picture of his life that can be used to determine whether or not he assaulted this woman in highschool?
He admitted to partying a lot. Saying he never blacked out is equivalent to "but I didn't inhale". There are several women willing to ruin his reputation and life by alleging sexual misconduct. That is enough for me, and it should be enough for everyone. If that isn't enough to budge the calculus of certain people then no amount of circumstantial evidence is, certainly not the fuzzy kind you'd get from an investigation. Be real.