When it comes to knives/blades, if all your strikes were below the belt and your defense consists in not being the attacker in the first place... You can easily argue that yes you stabbed him on purpose yes, below the belt, to not hit vital organs/not kill him. You hit in the ass/legs/thigh typically, or forearms not the chess not the neck/face And regardless of the outcome, in case if he died for instance, it proves that your intent wasn't to kill him in the first place, because you took care of NOT targeting vital organs... It's hard to charge for murder in that context and again you didn't start it... You aren't guilty of assault in the first place. Now, that being said, there are areas in the legs that can turn deadly if severely damaged, the femoral artery typically https://pic8.co/sh/OqUYrx.png Can you kill with a low kick? Well in theory, if you shatter the femoral artery yes But well... What are you kicking? A 5 years old? A grandmother?