I wonder if it can be shown how "old" the semen found in her was?
Without having gone back to check the wording of the NC rape shield statute, I believe it would be allowable into evidence here if the defense attorneys can convince the trial judge that the prior sexual activity is probative of the issue as to how the injuries to her genital area were sustained, and the probative value in this case whould outweigh any prejudicial effect, and I would expect a judge to so rule.
It seems that if the sex happened on the same day as the "alleged" crime, it wouldn't be all that "prior" and should be allowable. The evidence of that sex is critical evidence in the case and the guy is part of that evidence, so to speak.
This guy could've been the one that raped her (IF a rape even occurred). And he will be questioned by the police and then maybe brought before a grand jury like the other guys were.