Every mass shooting has three elements: the killer, the weapon and the cultural climate. As soon as the shooting stops, partisans immediately pick their preferred root cause with corresponding pet panacea. Names are hurled, scapegoats paraded, prejudices vented. The argument goes nowhere.

Let's be serious:

• The Weapon

Within hours of last week's Newtown, Conn., massacre, the focus was the weapon and the demand was for new gun laws. Several prominent pro-gun Democrats remorsefully professed new openness to gun control. Sen. Dianne Feinstein is introducing a new assault weapons ban. And the president emphasized guns and ammo above all else in announcing the creation of a new task force.

I have no problem in principle with gun control. Congress enacted (and I supported) an assault weapons ban in 1994. The problem was: It didn't work. So concluded a University of Pennsylvania study commissioned by the Justice Department. The reason is simple. Unless you are prepared to confiscate all existing firearms, disarm the citizenry and repeal the Second Amendment, it's almost impossible to craft a law that will be effective.

Feinstein's law, for example, would exempt 900 weapons. And that's the least of the loopholes. Even the guns that are banned can be made legal with simple, minor modifications.

Most fatal, however, is the grandfathering of existing weapons and magazines. That's one of the reasons the '94 law failed. At the time, there were 1.5 million assault weapons in circulation and 25 million large-capacity (i.e., more than 10 bullets) magazines. A reservoir that immense can take 100 years to draw down.

• The Killer

Monsters shall always be with us, but in earlier days they did not roam free. As a psychiatrist in Massachusetts in the 1970s, I committed people – often right out of the emergency room – as a danger to themselves or to others. I never did so lightly, but I labored under none of the crushing bureaucratic and legal constraints that make involuntary commitment infinitely more difficult today.

Why do you think we have so many homeless? Destitution? Poverty has declined since the 1950s. The majority of those sleeping on grates are mentally ill. In the name of civil liberties, we let them die with their rights on.

A tiny percentage of the mentally ill become mass killers. Just about everyone around Tucson shooter Jared Loughner sensed he was mentally ill and dangerous. But in effect, he had to kill before he could be put away – and (forcibly) treated.

Random mass killings were three times more common in the 2000s than in the 1980s, when gun laws were actually weaker. Yet a 2011 University of California, Berkeley, study found that states with strong civil commitment laws have about a one-third lower homicide rate.

• The Culture

We live in an entertainment culture soaked in graphic, often sadistic, violence. Older folks find themselves stunned by what a desensitized youth finds routine, often amusing. It's not just movies. Young men sit for hours pulling video-game triggers, mowing down human beings en masse without pain or consequence. And we profess shock when a small cadre of unstable, deeply deranged, dangerously isolated young men go out and enact the overlearned narrative.

If we're serious about curtailing future Columbines and Newtowns, everything – guns, commitment, culture – must be on the table. It's not hard for President Barack Obama to call out the NRA. But will he call out the ACLU? And will he call out his Hollywood friends?

The irony is that over the last 30 years, the U.S. homicide rate has declined by 50 percent. Gun murders as well. We're living not through an epidemic of gun violence but through a historic decline.

Except for these unfathomable mass murders. But these are infinitely more difficult to prevent. While law deters the rational, it has far less effect on the psychotic. The best we can do is to try to detain them, disarm them and discourage "entertainment" that can intensify already murderous impulses.

But there's a cost. Gun control impinges upon the Second Amendment; involuntary commitment impinges upon the liberty clause of the Fifth Amendment; curbing "entertainment" violence impinges upon First Amendment free speech.

That's a lot of impingement, a lot of amendments. But there's no free lunch. Increasing public safety almost always means restricting liberties. We made that trade after 9/11. We make it every time the TSA invades your body at an airport. How much are we prepared to trade away after Newtown?

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