Jumping off of these posts. To my knowledge, they released cause of death, but they still have not released whether or not she was sexually assaulted. Quoted from this article:
http://www.huffingtonpost.com/2014/...annella-strangled-missing-girl_n_5774456.html
"However, authorities said she didn't have any clothing on her lower half and they are looking into whether she was the victim of sexual assault."
Having no clothing on her lower half, and his stealing himself underwear leave me little doubt.
It is my opinion, based on other cases I have seen, that they will not charge him with any sexual assault until they are sure what kind of sexual assault occurred, if any. There are many (sad to say) different types of sexual assault. Any, some and/or all of them could have been visited upon the poor girl. Using pure conjecture, there could have been evidence of a previous assault of some kind, sexual or other. IMO, they will not charge regarding this until they have all the information to charge EVERYTHING they can.