I have a wait and see attitude on this....
I think Great Van Sustern nailed it on the head with this one. She says it doesn't take 17 days. If his DNA is in her and it's his word against hers you put it to a jury and let them decide who's credible. My guess is that's whats happening here.
Remember that boys when you have sex with these girls today. If she says you raped her the DA is practially OBLIGATED to file charges against you. Period.