By Beth Schwartzapfel
On a humid day in April 2009, the sound of gunfire drew police to a suburban home in Jefferson Parish, La. Officers found no shooters or victims — just an empty backyard littered with shell casings. In an area with the nation’s highest gun death rate, the incident seemed pretty minor. “Garden-variety case,” is how one detective described it.
Still, the casings were taken to the crime lab and entered into a huge federal database run by the Bureau of Alcohol, Tobacco, Firearms and Explosives.