But the bottom line is that even if she tripped and fell and hit her head or he hit her with a rock, and she was already injured/dying, he finished her off by strangling her, and he's admitted that he killed her in his deathbed confession. You cannot strangle yourself, therefore it's a homocide. (I guess that he could have hit her with a rock after he strangled her, but they still determined that her cause of death was strangulation). It's not uncommon to have more than one method of death, but usually one is primary.