I think they've found more than just her blood tbh. Don't want to say here as it could be really upsetting.
I do think he did it, I think a lot of why people are confused and things not tying up is because not a lot of information has been released, they're trying this new American way to make sure the trial isn't hampered. I think that too is why they're hitting him with the PCoJ charge - they're hitting him with everything they can. What he's being charged of is a heinous crime and (assuming he's done it) the longer he's put away for the better.
I'd be very interested in hearing Tasha and Welshcowgirls theories too.