Unless he raped her there won't be any admissible DNA in this case - he was a family member, he would have visited her, she was found in her grans house so on and so forth. Funny how people tell me they don't believe in vigilante action when I'm ripping the police, then we have how many saying we should kill a man for a crime.
You've all made you're minds up already, how do we know it wasn't the gran, maybe by accident after a fight, and he ran away for different reasons?