Police agencies routinely resell or trade in their used duty weapons, a practice that has contributed to more than 52,000 police guns turning up at crime scenes since 2006, according to newly obtained data from the ATF.

CBS News, in partnership with The Trace and Reveal from The Center for Investigative Reporting, reviewed records from hundreds of law enforcement agencies across the United States and found that many had routinely resold or traded in their used duty weapons – a practice that has sent thousands of guns into the hands of criminals.