http://www.huffingtonpost.com/2013/01/20/gun-control-debate_n_2514918.html
excerpt
SAN FRANCISCO/NEW YORK, Jan 20 (Reuters) - In tracking down illegal weapons, the smoking gun may not be a gun at all.
Bullets are one thing Sacramento Police Detective Greg Halstead can count on to root out weapons that otherwise would be impossible to find. They are also largely missing from the gun control debate in Washington.
Since 2008, California's capital has required ammunition dealers to take names and thumbprints of bullet buyers. They send the information electronically to police computers, which compare the names to an FBI criminal database.
Halstead begins his day looking at a list of buyers, picking out the ones who aren't supposed to own ammunition - or guns. The thumbprint left by each prohibited buyer is nearly perfect evidence of crime.
"The ammunition case is a slam-dunk solid," said Halstead, who regularly turns up illegal guns at homes he otherwise would have no reason to search. Some 154 felony convictions and 92 misdemeanor convictions have resulted so far.