This question is problematic because the goal in a self-defense situation is to end the threat. One claim is that "many" threats are stopped simply by producing a weapon. The general theory of self-defense (both moral and legal) includes a notion that the fight is over if the attacker retreats; a self-defense claim crumbles if the defender continues the fight. So consider the scenario of Bernard Goetz: he felt the threat; he produced his revolver; and he shot at the threat. If he hadn't pulled the trigger, and the boys backed off, we probably never would have heard the story. It's unlikely that he would have gotten off the train, found a cop, and related the incident. And if he did, perhaps he wouldn't have mentioned his gun?
How often does that happen? I have no idea. Some studies have been done, but they fall prey to all the problems we've been talking about on that other thread: what's the representative sample? Are people telling the truth? Is the person performing the study already biassed? So: a big chunk of salt there.
> How many such cases are there which have prevented such instances
It's probably unknowable. One number that can be used to consider the more general question is the number of homicides that are ultimately determined to have been 'justified' -- this is almost always because of a self-defense claim. In 2005 there were ~650 such homicides, nearly all with a gun, and about 60%/40% cop/non-cop. So: 250/year is about the rate for citizens, and it's pretty steady over the last decade or so.
Is this a significant number? Beats me. But I'll say this: "gun battles" -- armed attacker vs armed defender -- are very rare. Almost all gun violence is lopsided with the attacker having the drop on the defender from the get-go. How many of the ~7500 handgun homicides each year in the US involve the killing of an armed defender? Beats me, but I'd bet it's not very many.
My beliefs, based on nothing more than having read what I can find on the subject, are:
- There are a large number of concealed permit holders in the US - A significant number of them don't carry on a regular basis - A significant number of those won't ever present their weapon - Having a permit and getting yourself killed is incredibly rare
So for me, you can't say much about this line of reasoning one way or the other. I will relate an anecdote just to show how complicated it can get.
A guy I know had an abusive ex-boyfriend. Yadda yadda yadda, one day the guy shows up at the ex-girlfriend's house and is yelling outside. Making threats. No one inside stupid enough to open the door. Eventually the guy goes away. Comes back with an ax. Bangs on the door, wants in, wants to do harm, says so clearly. Starts chopping at the door, gets the blade through a bit, keeps chopping. Girlfriend freaking out, and the guy I know isn't sure what to do or how serious this is. Getting more serious all the time, tho. Has met the guy before, knows he's big and strong, but who expects the front door to get axed? So he gets his pistol and waits. Finally the door comes off the hinge and in comes the ex-boyfriend, spitting mad, full of adrenaline, and holding an ax.
Stop. What's on your mind if you're in this situation?
The guy I know yells at the ex-boyfriend and points his pistol at him. Big guy with an ax, he sees the light. Runs away, down the street. Everyone comes back down to earth, things are better now, right?
10 minutes later a tactical team shows up. Seems the ax-man called 911 about "a crazy guy with a gun, he's probably hopped up on meth" ...
What do the cops know? Not much. How true is my story? I have no idea. What happens next? You betcha. They take him down, arrest him, book him, take away his firearm, make him post huge bail, make him hire an attorney, yadda yadda. Do they have a choice in the matter? I doubt it.
/jordan