According to the lawsuit, MA is on tape with the SDPD admitting to having consensual sex with the girl. If that is true, and it better be for a lawyer to put their name to it (under penalty of perjury before the Court), then he is in fact guilty, by statute, of rape because she was under 18 and he was over 21. At that point, he can offer the affirmative defense that he did not know she was underage. In other words: yes, he is presumed guilty by virtue of the relative ages, and he has to prove his innocence by weight of evidence.
This was actually an easy decision.