In many countries there is a general principal of law that says that you must take victims "as you find them" (sometimes refered to as the "eggshell skull principle"). Basically it means if you shout BOO at someone and it turns out they have a weak heart and drop down dead you are still considered guilty of manslaughter even though you had no way of knowing that they had such a weakness.
Take Your Victim As You Find Them | ICBC Personal Injury Claims Lawyer Erik Magraken | Victoria & Vancouver Island BC
Obviously you can claim you didn't intend to kill them and that should be considered in mitigation but you are still guilty. It's not the victims fault that they have a weakness.