1) This bit is weird.
2) Everything else seems like he could be framed. Take his car. Take his phone. Sprinkling some of his DNA on the knife. Etc. Given that he was a PhD student in criminology his slip ups (?) sound intentional. He can't be that ignorant of tech and crimes, can he?
3) I don't understand how he did it alone. According to the reports I've heard, two of the (female) victims were sleeping in the same bed. He got them both with no screaming? And then two more with no screaming? And the eye witnesses saw a stranger - in the middle of the night? - but weren't the least bit suspect and didn't check on their roommates the next morning?