I don't think there is any proof that we know of that the accused was actually in the home for an hour or so after the attacks. Nor is there any proof he cleaned himself up afterwards (correct me with a new story if I'm wrong). I think the idea that he was there for so long after the murders has come from the police giving a time frame for the events. Having seen how close these houses are together, I cannot imagine anyone sticking around after the yelling that was heard by the neighbour. Also surely no one is careless enough to spend time cleaning themselves up then leave a blood trail in the street.
Also I wouldn't think that he would be sleeping over, or even telling anyone he was sleeping over. CR had a boyfriend, having another male sleep over let alone your boyfriends best friend, seems like a very strange thing to me. Can you imagine the troubles that would cause in the teenage world. Besides we don't actually know for a fact that he was dropped off there, this has been said by people on this and other forums, but never released as a fact by the police.
Also to confuse the situation even more, people have stated he was dropped off, then there is the sighting of the ute in the street which one person got out of. A poster has since said that this ute has "disappeared". Surely we are not going to imagine that the accused was dropped off by someone, then an hour before the murders another vehicle totally unrelated to the crime stops and someone gets out, but after the fact never comes forward to clear their name. It seems to me that the white ute is key, either the person who dropped him off drove the white ute, or there is a possiblity of someone else's involvement in the crime.