A recurring theme on the board is shooting in response to an unarmed attack. Though I don't know every poster's background, some of the undercurrents concern me. So, this post on the basics involved. The material in it is drawn primarily from Ayoob's course on the judicious use of deadly force (by permission) and my work in LE covering use of force. First, the justification for the use of deadly force. It has to be based on a reasonable fear for your life. That means that you have to be able to articulate that your opponent has the means, the opportunity and the intent to kill you or do great bodily injury. (Some refer to ability, opportunity and jeopardy. I think the way I was originally taught is clearer.) Opportunity is the delivery system--can he make good on his desire. Talking about unarmed assailants, that means that they have to be close, and not on the other side of a locked door or 8' chain link fence. Close doesn't mean touching, but in practical terms, it likely will. You should consider the practicality of your method of carry and your ability to present and employ the firearm at those tight distances. It's highly likely that you're going to have to fight your way to the gun. Intent talks to the actual plan of the opponent. You don't have to be a mind-reader, but you do have to be able to articulate what made you believe that a potentially lethal assault was about to be delivered. Documentable knowledge about pre-assault clues is a plus here. Means refers to the method of delivering lethal or near-lethal force. I saved this for last, because it's where the issue arises when talking about an unarmed adversary. The totality of the circumstances matter, but you need to describe some disparity of force between you and the other guy. When we're talking average guy against average guy, you're going to have a very hard time explaining that he was a lethal threat. Why? The DoJ figures have some 2.4 million simple assaults occuring every year. http://bjs.ojp.usdoj.gov/content/pub/pdf/cv10.pdf That's obviously a lot. But when we look to homicides, there were only 745 as a result of beatings in 2010. http://www.fbi.gov/about-us/cjis/uc.../crime-in-the-u.s.-2010/tables/10shrtbl08.xls It's on you to explain how that 0.31% ratio rises to a reasonable fear in your case. So you need a disparity in force that you're using the gun to equalize. That can be petite woman vs. monster man, it can be arthritic gandparent vs young banger, it can be a significant disparity of numbers. Or it can be a disparity as a result of situation--you're down and can't get up, you're hit and feel yourself blacking out. Ayoob, who should know, says that there isn't any large body of research on what match-ups are "fair" and which support the use of deadly force. My own student shot in a 3:1 situation after taking blows to the head and was prosecuted vigorously (2 trials, both that ended in hung juries. No conviction, but more than one juror wanted to send him to prison.) This all comes back to the reasonable fear that I referenced above. Not all fear is reasonable. Reasonable fear can be articulated through means, opportunity and intent as described. Terror, or naked fear, or unreasonble fear doesn't make the grade. If you're relying on stories of one-punch deaths to justify your actions, you've got to overcome that 745:2,400,000 ratio, and you have to deal with the mind of every juror that's been in schoolyard fight or seen a boxing match. Naked fear is that "well, it could happen" thing; you have to avoid it. Reasonable fear is "it's happening now, and I know why". Anyway, I hope this sparks research and consideration. Please let me know if I've been unclear on anything.