Whenever a school shooting occurs, as in Pennsylvania Amish country last week, or in Colorado and Wisconsin last month, or in Vermont and North Carolina the month before, we understandably seek answers -- to the wrong question.

		Kristin A. Goss is assistant professor of public policy studies and political science at Duke University and author of "Disarmed: The Missing Movement for Gun Control in America," published this month by Princeton University Press (kgoss@duke.edu).

The press and public focus on motive -- what would possess a milk truck driver or drifter or teenager to kill -- when we should be asking, "Where do dangerous individuals get their guns?"

Amazingly, amid the rash of killings in our schools, Congress has been quietly working to make answering that question even more difficult.

Just last month, the House Judiciary Committee approved a bill that would bar the Bureau of Alcohol, Tobacco, Firearms and Explosives from disclosing trace information about the hundreds of thousands of guns used in crimes each year. The bill, backed by the National Rifle Association, is a political move to derail lawsuits filed by gun-control advocates against scofflaw gun dealers.

But the gag order would affect much more than the lawsuits, which are in legal limbo anyway. The bill would deprive gun-control advocates, scholars, state and local law enforcement officials and even members of Congress of vital information about the black market for guns operating in our midst.

A second NRA-backed bill, passed by the House to "modernize and reform" the ATF, would make gathering gun-trace data even more difficult. Federally licensed gun dealers would no longer be required to keep sales records organized according to regulatory protocol. In practical terms, according to former ATF officials who wrote Congress to oppose the bill, keeping records in disarray would make it impossible for firearms inspectors to ferret out lawbreakers.

Complicated, highly technical bills about data and record keeping don't inspire public passion or prompt marches on Washington. But the data that the government collects and the laws that govern the data's disposition are vitally important to the success of citizens' movements.

In my book on gun politics in America, I argue that one reason gun-control groups have been unable to mobilize grassroots sympathizers is because their opponents have blocked federal agencies from collecting and disseminating information that would help them make their case.

To understand the political importance of authoritative government data, ask yourself this: Where would the anti-tobacco movement be today if cigarette companies had prevented the surgeon general from documenting the health hazards of smoking? Where would the anti-drunk-driving movement be had beer companies stopped the National Highway Traffic Safety Administration from counting alcohol-related deaths?

But unlike their counterparts in the anti-smoking and anti-drunk-driving movements, gun-control advocates have been on the losing end of a decades-long political battle over government data.

This year's House bills are just the latest chapter in a history of assaults on the ATF and its efforts to quantify America's illegal-gun problem. Another, and in some ways more interesting example, involves the U.S. Centers for Disease Control.

In the early 1970s, a handful of medical professionals began arguing that gun violence was a public health issue. A decade later, the CDC established a small program to study gun violence from this novel perspective.

Perhaps because of its size (about 1/10th of 1 percent of the CDC budget), the NRA was slow to recognize the threat posed by the CDC and its research. But when the public health approach started gaining traction in Washington, the NRA worked to stop the CDC's violence program dead in its tracks, eventually lobbying Congress to eliminate the program entirely.

To stave off elimination, the CDC stopped funding outside researchers, but that was not enough. In 1996, Congress stripped the gun-violence program of its funds and stipulated that no injury-prevention dollars could be used to "advocate or promote gun control," a provision that remains in place.

The NRA and its congressional allies understood all along what gun-control groups were slow to realize: Letting good data fall into your opponents' hands is a bad idea. Getting Congress to prevent citizens groups from knowing the truth about illegal firearms markets may be the gun lobby's idea of smart politics, but it is terrible policy.

Where do killers get their guns? We may never know.