Beyond all questions of politics is a more basic question of efficacy. What exactly might be done to prevent mass shootings, especially at locations such as schools? In the wake of the Giffords shooting by Jared Lee Loughner, there were many calls for institutionalizing more people who seemed mentally unhinged and potentially violent. The same thing is happening now, for obvious reasons (by various accounts, none of which has been fully substantiated yet, presumed gunman Adam Lanza was unhinged). As Reason’s Jacob Sullum wrote regarding Loughner, even the most vociferous propopents of locking up potential killers grant that maybe 10 percent of schizophrenics become violent. Academic studies of presumptive detention of the mentally ill suggest that mental health professionals do about as well, and sometimes worse, than regular people in figuring out who exactly is going to go postal. Such results should temper any and all calls to start rounding up more people in the name of protecting innocents.

The general decline in gun-related violence and the inability even of mental health professionals to identify future mass killers should be the essential starting points of any serious policy discussion generated by the absolutely horrific slaughter at the Sandy Hook Elementary School in Newtown, Connecticut. We should also add a third starting point: Few good policies come from rapid responses to deeply felt injuries. Many of the same people who are now calling for immediate action with regard to gun control recognize that The Patriot Act, rushed through Congress in the immediate aftermath of the 9/11 attacks, was a terrible piece of legislation that ultimately did nothing to protect Americans even as it vastly expanded the state’s ability to surveil law-abiding citizens. There’s no reason to think that federal, state, or local gun control laws promulgated now would result in anything different.

If hard cases make bad laws, it’s even more true that rare crimes make terrible public policy.