'Jujitsu' means gentle art, but it's all about breaking arms and snapping necks. I took Judo as a kid as well, chokes holds are permissible amongst the older classes, and I learned a few as well as some escapes. It's really just a sparring version of Jujitsu and black belt could easily strangle someone who didn't know how to defend himself.

Still, this is a lot of speculation and if he strangled her, where did the blood come from? I think that it is quite likely that he killed her, but not with a choke-hold.