Gun tracing is a method for identifying a gun’s sequence of ownership from manufacture to first retail sale. When law enforcement recovers a firearm, it may send the gun’s serial number and other identifying information to the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), which uses a system called eTrace to identify the last licensed seller and, from there, the buyer. According to ATF, crime gun tracing information is used:

1. To link a suspect with a firearm in a criminal investigation
2. To identify potential traffickers, whether licensed or unlicensed sellers of firearms
3. To detect in-state and interstate patterns in the sources and kinds of crime guns

Gun trace data used to be available to the public, but a 2003 rider on the Appropriations bill, known as the Tiahrt Amendment, blocked ATF from releasing the data.

Gun trafficking is the unlawful movement of guns from the legal market to the criminal one. Trafficking can be facilitated by both licensed and unlicensed dealers. A small number of gun dealers are responsible for diverting guns to the criminal market. According to the last available data, about 90% of crime guns were traced back to just 5% of licensed dealers.

Bulk sales and private sellers facilitate gun trafficking: traffickers often buy large quantities of firearms and then take advantage of private sale loopholes to move those guns into the criminal market.

A straw purchase is when someone purchases a firearm for another person’s intended use. The straw purchaser fills out the paperwork and completes a background check at a federally licensed firearm dealer. Straw purchases undermine both the background check system and the gun tracing system, and they allow guns to fall into dangerous hands. Straw purchases are illegal and a major source of trafficked firearms.

“Time-to-crime” is the amount of time between the retail sale of a firearm by a federal firearms licensee (FFL) and its recovery by law enforcement. ATF considers a time-to-crime of less than 3 years as a potential indicator of trafficking. When a significant number of crime guns with a short time-to-crime are traced back to one particular FFL, ATF considers this an indicator of potential illegal activity such as gun trafficking.

A federal firearms licensee, or FFL, is an individual or company licensed by ATF to engage in the business of selling firearms.

PLCAA, or the Protection of Lawful Commerce in Arms Act, is a federal law that provides the gun industry with special protections from civil lawsuits, at the expense of victims of gun violence who would otherwise be entitled to compensation for the damages they have suffered. PLCAA removes key incentives for the gun industry to adopt life-saving business practices and instead provides cover to irresponsible gun dealers who supply the criminal gun market. This small minority of gun dealers profits from dangerous business practices with no accountability to their victims. No other American industry enjoys such civil immunity.

In 2003, the Tiahrt Amendment was first added to a bill funding the ATF and limited the ATF from publicly disclosing information from the Firearms Trace System database. Over time, the Tiahrt Amendment has been interpreted to shield the most negligent gun dealers from public scrutiny while also depriving the public of key data to help stem the flow of illegal guns.