Motive was likely sexual aggression. No complex motive is required.
On lack of DNA evidence at accused home and victim's home. We have to remember the police check "key" areas, not inch by inch. Additionally, of course the scene of the crime will have far more cross between victim and accused than his home. She was never there, therefore it would have to be transference... I don't think there was significant amount of blood etc, so it's not like he had much to clean other than his body which is explained by the shower.
I would echo what others have said - we have to remember we are only getting snippets via Twitter. So of course we are not making a fully informed opinion vs that of a jury. However we are absolutely entitled to do that, we don't all have to follow jury rules in our personal lives and on WS.