“When does it stop being self defense?” - not at them turning around. And I’d say you have a right to shoot them till the moment the police come to take over the situation / provide safety for you. Running after someone who is like 500m away to shoot them wouldn’t be self defense anymore obviously. And again - “self defense” isn’t a black and white situation. It’s grey enough where each case needs to be determined individually. But the “bias” belongs with the person whose house they broke into, not with the burglar. A burglar killing someone and saying “they had a gun!!” is 100% murder. A person overreacting / crossing a “line” in self defense deserves leniency if not straight up immunity.