Too often, when people imagine dealing with a deadly threat, they visualize an attacker who is clearly armed with a deadly weapon. The reality is often far from that image. Poor lighting may prevent us from seeing just what, if anything, the person has in his hands. Further, the person making threats and advancing may have their hands in their pockets. Do they have a knife? A gun? Do they just plan to beat you with fists?
As armed citizens, we must only respond to a threat. We can’t initiate the action. We must decide what, if any, threat there is. And then we must decide how to react to it. In other words, if the crook does “X” then I will do “Y”. We call that the mental trigger.
And that response need to not only effectively stop the situation but it must be an acceptable response under the law. If a man comes at you to beat you with his fists it might not be appropriate to shoot him. “He scared me!" may not turn out to be a good legal defense.
Another real-world example might be the neighborhood bully who is standing across the street, 25-30 yards away, and threatening you with a baseball bat. You honestly believe his threats are real. Should you shoot him? Should you wait to respond until he is in striking distance with the club? At what point can you lawfully respond to his attack? Knowing what your options are and knowing what is considered a lawful response helps you establish your mental trigger for dealing with the attack.
It takes a good deal of training and a good deal of thought to establish an effective mental trigger. It is generally not a good idea to wait to establish a mental trigger in the middle of the actual chaos and stress when your judgment may not be at its best.
In the case of the man who is advancing and won’t take his hands out of his pockets, I would be considering that I might need to rely on some less-lethal defensive tool. In the case of the man with the club, it might be a good idea to wait to deploy the defensive firearm until he has reached the point of being able to reach me with that club. And, in both cases, the defensive shooter should also have considered the use of cover or just exiting the scene. In any case, we should not hurt him because we can, but because we have to. “If he does this, then I will do that” is the mental trigger.