my understanding from the reports in the media is that there are potentially three sex partners that eventing from that party.
(she could argue they wore condoms too which woudl negate leaving anything behind)
I think the DNA is to elimanate all but the absolute minimum.
That is based on her account of what happened- that three lax players dragged her into the bathroom and raped her. But the players have argued that none of them even had consenual sex with her- she came in drunk and bruised up, she and her partner danced for about three minutes, they then locked themselves in the bathroom for about 30 minutes, then they left with the $800. So if the player's account is accurate, there should be no semen from the lax players found inside of her.
she could argue they wore condoms too which woudl negate leaving anything behind)
That's possible, although I agree with the defense attorneys that it seem hard to imagine that three drunk players were able to rape her vaginally, orally, and anally without leave any DNA. It is also hard to imagine that she was raped orally yet wouldn't be able to tell whether they used a condom or not.
So why take samples? According to what I read, she went to the hospital. I assume they took a sample from her, which, I presume, is why they took samples from the players.