Weren't there multiple DNA samples found under her nails?
Defense questions investigator on the stand: How were those other samples picked up? Was she raped by these other people?
Investigator of course answers "No" and explains to the jury all the ways DNA can be transferred under the nails.
Defense says, so my client could have transferred DNA in these same ways, correct?
Investigator goes Duhhhhh, yeah, but....
Game, set, match.
Good job!