The general principle, in the US, is quite simple.
You may use the force reasonably necessary to safely resolve the situation.
Sounds simple. Let's look at the words.
- Force: any means of imposing your will on someone. That includes simply being there (usually for cops or security more so than a private individual -- but it can apply if that private citizen involves themselves in someone else's problem) or saying no, up to any means of causing grievous bodily harm or death. Lethal force ain't limited to guns; it includes knives, baseball bats, choke holds, punches to the throat, throws on hard concrete... anything that is reasonably likely to cause serious bodily harm or death.
- Necessary: Key issues here are Intent, Means, Opportunity, and the oft neglected Preclusion.
[*=1]Intent: Did the attacker intend to do you harm? Assuming a decent self defense scenario, this is often a given. But you have to take it into account, because if they lacked the intent to do you harm, you can't do anything to them without becoming an assailant yourself. And it applies in a Monkey Dance -- because in some cases, the last thing the players actually want is to fight. They're just putting on a show for their friends and the crowd.
[*=1]Means: An actual capability to do harm. Weapons, including unarmed weapons like fists and feet. Again -- most self defense situations, this is generally a given. They've shown a weapon, or they've grabbed you... but you need to be able to articulate how they were going to carry out their intent to do you harm. You can't shoot someone 15 yards away who says he's going to shoot you if he doesn't have a gun and you have no reason to believe he has one.
[*=1]Opportunity: Are they in a position to do what they threaten? Someone threatening to choke you to death from a couple hundred yards away lacks the opportunity to carry out their threat (unless, of course, they're Darth Vader). Yep, again, in a good self defense situation, this is given.
[*=1]Preclusion: Your use of force was the only option available to you that would likely have ended the situation safely. Especially important in lethal force. Stand your ground laws shift this a little -- but you still have to be able to say that you were in the right and didn't create the situation.
- Reasonable: Would that mythical creature, the reasonable person, conclude that your force was appropriate and proportional to the threat presented? Can you show why you needed to hit, kick, lock, or shoot that person -- and that other options wouldn't have been likely to resolve the situation effectively? (Yeah, some overlap here with preclusion.) You can write books about reasonableness -- but generally speaking, if the force you use is about the same or a little more than was being threatened or used, you're likely to be in the right neighborhood. You can likely punch someone who's grabbing you -- but need to explain more if you shoot them. If they get a weapon, you're almost certainly OK (assuming you were in the right in the first place) getting one of your own. But if you shoot someone waving a Nerf sword?
- Safely resolve: What's your role? My job as a cop means that "safely resolve" typically means subdue and arrest. For a private individual, your role in self defense is to escape and get help -- not effect an arrest. Generally, "safely resolve" means get out of there without any more injury than you sustained in the initial attack. Not get even with the bad guy.
Cases of one punch kills, or freak incidents where a guy falls and hits his head on a rock tie into one other principle: You take your victim as you find them. Unknown to anyone, the guy has a dissecting aorta, and your punch is the final straw... You might be charged with some class of homicide. Same thing if he falls and hits his head.
Oh... yeah... Charges. Depending on what happens, you may do everything "right" in defending yourself, but may still find yourself arrested. Especially if you kill someone. That's when you go back to that local attorney you consulted, as was advised by Carol and frank raud, and you hire him. Unless you've learned of a better attorney to hire. Then you hire that guy.
