My specific comment, though, has to do with the fact that he claims to have drugged her, although the autopsy showed otherwise.
It suggests that he made up at least part of his story. I'm also going to go out on a limb and predict that his DNA will end up not matching: the DNA story is not sourced, and the timeline between arrest and "positive match" sounds suspiciously short.
He also said he picked her up at school that day. It was Christmas vacation, she wasn't in school.