Why ghost guns are so easy to make — and so dangerous

The shocking broad-daylight shooting of UnitedHealthcare CEO Brian Thompson on Dec. 4 was carried out with a homemade firearm that alleged shooter Luigi Mangione may have created with a 3D printer. The increasing use of such weapons, often called "ghost guns," has raised troubling new questions about the easy availability of homemade firearms and the challenges they pose to both public safety and the ability of law enforcement to solve crimes.

How do ghost guns work?

Ghost guns are "firearms that are privately assembled and untraceable," said NPR. Some are created more or less from scratch using 3D printers, and others are sold as partially assembled "kits" to individuals, to avoid assigning the weapon a traceable serial number. That's because the individual components of a gun "are not subject to any of the federal regulations that govern firearms sales," including background checks, said PBS News.

The use of a ghost gun in Brian Thompson's killing was hardly a new development. Gun kits allowing people to build their own weapons by simply completing a few simple assembly steps at home have been around since the 1980s, and that is still how many people obtain their ghost guns. But the ease of creating homemade firearms increased dramatically with the rise of 3D printing in the 2010s. 3D printing is a "manufacturing process in which material is laid down, layer by layer, to form a three-dimensional object," said PC Mag. 3D printers, therefore, can use that process to "turn digital files containing three-dimensional data" into a variety of items. As costs have fallen over the past 20 years, 3D printing is "no longer a novelty technology," said Steve Lohr at The New Yorker.

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In fact, anyone can now buy a small 3D printer for under $200 online and use it to create everything from guns to food. And the "vast majority of people assembling a ghost gun are legally allowed to do so," said CBS Philadelphia. That means that this type of ghost gun is increasingly "falling into the hands of individuals who should not have access to them, including young people and violent extremists," said The Soufan Center.

Why are they a problem?

Guns manufactured in the U.S. or imported from abroad are "​​legally required to have serial numbers," which are the "critical piece of information that law enforcement agencies use to trace the gun from the manufacturer to the gun dealer to the original buyer," said The New York Times. Without the ability to trace firearms back to individuals, law enforcement is deprived of one of its most significant crime-solving tools at a time when ghost guns are proliferating. "Because of their untraceable nature, we can't say for certain how many ghost guns are in circulation," said the Federation of American Scientists. But between 2017 and 2021, there was a "roughly tenfold increase in the number of ghost guns submitted to the ATF by law enforcement agencies for tracing," said CBS News.

The explosion of ghost guns used in crimes is a problem the Biden administration tried to address in 2022 with a new rule that made it "illegal for businesses to manufacture gun kits without a serial number and for a licensed gun dealer to sell them without a background check," said The Associated Press. Since the Biden administration's rule was enacted, "those trends have reversed" and recoveries of ghost guns have dropped in many major cities and states, said The Trace.

In October, the Supreme Court heard oral arguments in a case challenging the Biden administration's ghost gun regulations. The court "appeared ready to uphold" the rule, said SCOTUSblog, and a ruling is expected sometime in 2025. Ghost guns were not part of the Trump campaign's gun policy agenda, and it is not clear whether the incoming administration will uphold or rescind Biden's rule. But the "growing availability of 3D-printed guns represents a whole new threat" that the Biden administration's rules didn't address, said the Giffords Law Center to Prevent Gun Violence.