Thankfully the police here suspected the husband (ex - supposedly reconciled) right away. They re-inforced a previous restraining order on him so that he couldn't even visit her in hospital. As it turns out they had great foresight and he and his mistress have now been detained on attempted murder charges. No doubt given the chance he would have turned off her life support.
In any murder case, the spouse or family member is usually the first one authorities deduce as the murderer.
How's your court system there? Any risk of a court ordered euthanasia? Depending on her level of brain damage, she might need extensive therapy, and still might never recover. Here in the States, there's a movement well under way to exterminate people with severe cognitive disabilities.