When reporters asked Baltimore police and state agencies where the guns used in city crimes came from, no one could provide specific information.
"I can tell you that the vast majority, 95 percent plus, are committed with illegal guns," Baltimore police spokesman Anthony Guglielmi said. But he didn't use data to support that widely held assumption.
Local law enforcement agencies don't have that information because of a federal blockage of gun tracing data. Police also can't reveal what gun tracing data they do have because a federal law passed a decade ago shields most firearm tracking information from the public.
Gun tracing information was public until 2003, when Congress passed what is known as the Tiahrt amendment. Named after former Kansas Rep. Todd Tiahrt, a Republican, the law limits what information is publicly available for research.
At the time, the National Rifle Association and others argued that gun research studies using tracing information were biased against guns and that the data allowed unfair scrutiny of legal gun dealers and owners. Tiahrt has also said that the law aimed to protect undercover police and informants.
But the amendment has come under increased criticism as the national gun debate heats up since the Connecticut school shootings and the Colorado movie theater massacre. Mayors Against Illegal Guns, led by New York Mayor Michael Bloomberg, has called for its repeal.
The amendment is also seen as one reason President Barack Obama added increased gun research as a goal in the broad gun control proposal he announced last month. Gun research has slowed considerably since the Tiahrt amendment passed.
In 2009, Congress passed provisions pushed by Obama's administration to tweak the Tiahrt amendment and direct the Bureau of Alcohol, Tobacco, Firearms and Explosives to share more gun-tracking information with other law enforcement agencies. But that loosening didn't open the information dam that much.
According to an ATF guideline sheet, a law enforcement agency requesting federal firearm tracing information can only receive data limited to its jurisdiction for a "bona fide" criminal investigation. The goal of restricting the data is to make sure gun that tracing information — like fingerprints — doesn't land in the hands of "third parties" such as journalists and the public, the ATF stated.
Law enforcement agencies are also limited in what information they can maintain. The FBI is required to destroy background checks on gun buyers, and federal laws prohibit any national database that stores information on gun ownership, sales or manufacturing.
The gun trace data that is publicly available from the ATF includes annual state-by-state breakdowns on the total number of guns recovered by law enforcement agencies. In 2011 in Maryland, for instance, that includes the total number of guns recovered (7,680), the types of guns recovered and a map showing the states where the guns came from.
—Justin George