I could have stopped the Colorado massacre if I had a concealed weapon, BUT...

David Weigel, writing for Slate, asks if a brave citizen with a concealed weapon could have stopped the Colorado massacre, where 12 people died and 59 were injured. Wiegel is skeptical. However, he also interviewed a firearms instructor and NRA member, Greg Block, who says that yes, he could have stopped James Holmes.

Block says that if he were armed, he could have drawn and returned fire in just over a second. He would have ducked between the chairs for concealment. Holmes was armored, but Block would have gone for a head shot or the pelvic girdle. Of course, Block points out that the theater policy was to forbid concealed weapons - a vulnerability in his view. In his view, people should be armed, so that they can defend themselves.

It's true that being armed will improve my safety in any single encounter. Like Block, I have some military training. His proposed tactics are sound. But they miss the big picture.

Let's specify a simple equation: in considering firearms control policy, we want to think about

Deaths from mass shootings + deaths from individual confrontations + deaths from suicide or accident

Deaths from mass shootings
In a world where carrying weapons for self-defense is as common as the NRA wants it, there is likely to be more than one friendly responder at the scene of a shooting. In Colorado, it turns out that Holmes had his back to the screen, so no risk of a crossfire. However, consider the Gabrielle Giffords et al shooting, where Jared Loughner fired from within a crowd. A responder could have other civilians in his or her sights when sighting on Loughner. And if there were multiple responders, there would have been an instant crossfire. Other responders might be confused as to who was a friendly and who was the shooter. Very bad.

It's not just about being able to shoot straight. It's about knowing how to respond under fire - how to identify a target, how to remain calm under incoming fire, how to discriminate between enemy and friendly. The last bit is very hard. Even elite counterterrorism units don't always manage to save all the hostages. Less trained individuals will have even poorer performance in confused situations like a sudden firefight. They might hit friendlies.

And in this case, Block frankly sounds overconfident. His resume doesn't appear to indicate he has any actual combat experience. Neither do I. Even if you were an experienced combatant, though, you do not know for sure that you would have stopped Holmes. You'd have a good chance. But it's not a sure thing. Consider, Holmes had a vest. You return fire to his torso, knocking him back. You notice he is not being incapacitated, and you switch to the head, but heads are small. There is gas. People may be running. Holmes has no restrictions on returning your fire. And what if you were in the back of the theater, out of easy range of a pistol? Is the solution that everyone carries AR-15s around?

Furthermore, in a world where firearms are more common, then leakages from legal channels are more common. It is easier for criminals and people with mental illnesses* to acquire firearms. The number of total mass shootings increases. Even if you assume that friendly mortality per single mass shooting decreases, there are more mass shootings. Total mortality could well increase.

Deaths from individual confrontations
In a world where firearms are common, there will be more individual confrontations as well. These could be domestic disputes. These could be bar fights. These incidents would have been settled with fists or knives prior to this. In the NRA's world, it will be a lot more common to have these incidents settled with firearms. And firearms are more lethal than knives or fists.

If the accusations that George Zimmerman stalked and killed Trayvon Martin out of a sense of vigilantism are correct, then this is one example. But I don't think we need the accusations to be right: "justifiable homicides" are generally up significantly since the advent of the infamous "stand your ground" laws in several states. In a number of cases, the police have been unable to investigate the incidents since one of the witnesses is dead. The living witness - the person who shot first - may well have had reason to fear for his or her life. But the threat may not have been lethal. The incident may have been a mere accident, as in the drunk person who showed up by accident at Gregory Stewart's door and got shot (first paragraph of the last link). Or, frankly, it may have been a homicide but now there's no real way to know. Police are trained in proportionate use of force - your responsibility is to protect the peace, and lethal force is a last resort, and you respond proportionately. By the way, police are not always to good at proportionate use of force. They, too, misidentify threats or use disproportionate force.

Or, the individual incidents could be bona fide incidents of self-defense. An intruder breaks into your house. He or she has a knife or a gun. In that situation the first thought would be, if I had a firearm, I could defend myself better. And again, that's probably true for each individual incident. But in the NRA's world, it's probably a lot easier for those criminals to get guns. So, more criminals would be armed. And perhaps individual criminals or gangs of them would be more careful about going in armed, since anyone they find is more likely to be armed. You have an arms race. As with the mass shooting scenario, it may make you safer per individual incident, but it probably makes society less safe in aggregate.

In other words, in the NRA's world, there are likely to be more individual confrontations, and the mortality rate per incident is very likely to increase. Some of these will be entirely justifiable, like self-defense. But some of these will be escalations of a situation that should not have been escalated. And some of these will be entirely unjustifiable.

Deaths from suicide or accident
Many suicidal crises are short-term and self-limiting. Between 30 and 80 percent of suicides are impulsive. Most suicide attempts do not succeed. But in a world with firearms readily available, there will be more successful suicides.

Firearm accidents will also be more common.

Conclusion
Being armed would improve my chances of survival, and the chances of those around me, in each single encounter with a gunman bent on a mass shooting. But I am not on SEAL Team Six. I am not on a SWAT team. I am not stupid enough to think that I would necessarily stop a shooter within the first few seconds, and if one or more other people started to return fire, things would get bad. And if many people armed themselves, thinking that they would be safer as a result, the effects on society would be completely unacceptable.

Mass shootings are fortunately not that common. The United States  is becoming safer, in terms of violent crimes. We do not generally need to be armed to protect ourselves. The other option is that we don't carry firearms, we rely on the police and we carry non-lethal products like Mace. The alternative to the NRA's world is what they do in Singapore and Japan: it's impossible or nearly so to acquire firearms, so there are very few shooting deaths (and Singapore has the death penalty if you so much as discharge one, outside of police or military duty).

Or, given that individuals in the U.S. have the Constitutional right to have firearms, we restrict assault weapons, body armor and high capacity magazines. We impose stricter licensing, like we require background checks and regular testing. Fewer citizens will be armed. But so will fewer criminals. The mass shootings will at least be someone with a .22 caliber pistol and an 8-round magazine - .22 caliber pistols are significantly less lethal, and when the shooter is reloading he or she can be jumped by a bystander, or people can run, or something. Shooters will be less likely to have body armor. There will be fewer ancillary deaths. And, by the way, there are the police. We've put centuries of toil into building a civilization that can stand the test of time, one that has a functioning democracy and functioning institutions of public safety. We should trust them. We are not on the frontier.

Whether individually or societally, guns do not make you safer.

* Most people with mental illnesses are not dangerous. The issue is what happens when the ones who are dangerous get firearms, especially ones with high capacity magazines.

PS: A blogger critiques some responses to the shooting, saying that AR-15s are not as dangerous as hunting rifles in that while they can fire more rapidly, the bullets are individually less powerful. This blogger states that AR-15s are not military weapons. The latter point is true as far as it goes, in that AR-15s are semi-automatic (one trigger pull, one bullet, whereas the M-16, which is basically the AR-15 for the army, can fire fully automatic, albeit the rounds will hit the ceiling as the rifle kicks up with recoil).

However, contrary to what this guy implies, the AR-15 is demonstrably more dangerous than a hunting weapon. In an infantry engagement, especially one at the ranges we are talking about, what matters is how many bullets you can put on the target in the shortest time. Many hunting rifles are bolt action, where you have to reload the rifle by working the action before firing again. Further, the .22 caliber bullets from the AR-15 tend to tumble inside a human body when they hit. They can be very lethal. A .458 Winchester Magnum round has more muzzle energy as this guy states, but rifles firing that round will fire a LOT more slowly. Such rifles could, I suppose, legitimately be used for hunting (albeit this is a big game round, and a lot of big game is endangered). One could make the case that there is no legitimate need for law-abiding civilians to have AR-15s. They can be used to kill multiple people within a short span. If you are a law-abiding civilian and you expect to be caught in a gang fight, get out of dodge and call the police.

I mentioned in the last paragraph that a .22 caliber pistol is relatively non-dangerous. One might ask why, if the rounds are the same caliber as the AR-15. The answer is that AR-15s shoot bullets at 975 m/s. That's almost three times the speed of sound. .22 caliber pistols have muzzle velocities under the speed of sound, or about 330m/s.