The charges were dropped, not just because there was no evidence, LC, but because there was exculpatory evidence. The DNA evidence clearly belonged to none of the Duke LaCrosse players.
As I remember it the victim was raped with instruments and asaulted. Of course no DNA. Any DNA would be from her live-in boyfriend. Or perhaps the charge was assault, not rape? There was no trial. The examining nurses said that there was trauma to her vaginal area. I don’t call that exculpatory evidence. A trial would have brought this all out.