GUNSWhat Is Microstamping, and Can It Help Solve Shootings?

By Chip Brownlee

Published 26 January 2023

Laws to expand the technology’s use have passed in three states and the District of Columbia. But some are questioning its effectiveness.

When law enforcement investigates a shooting, the evidence left at the scene can make or break a case. In ideal situations, there are witnesses, surveillance video, and sometimes even a firearm and a suspect. Not all cases turn out that way. Often, investigators are left with only a victim and a few spent casings. 

But what if a handful of brass was all investigators needed to solve a crime? Enter microstamping, a process that imprints a unique identifier on bullet casings when they fire, theoretically allowing law enforcement to identify the firearm used in a shooting. The technology is celebrated by gun reform advocates, who say it could help solve more shootings, and laws to expand its use have passed in three states and the District of Columbia. It’s also garnered intense criticism from opponents who question its effectiveness and say it places an unnecessary burden on gun manufacturers and owners. The debate led one reader to ask:

How feasible is “microstamping technology” really? I’ve seen many gun safety sites claim it’s feasible, but I’m hearing the opposite elsewhere. I’m also wondering, should the technology come to pass, what if a criminal just steals casings that have your stamped cartridge from the firing range?

Below, we break down the basics.

First Things First: What Is Microstamping Technology? 
Microstamping uses lasers to engrave alphanumeric and geometric codes on a gun’s firing pin, the piece of hard metal that strikes an ammunition cartridge’s primer and makes it fire. When a firing pin is microstamped, it imprints its unique code on the cartridge. This code is tiny, but when viewed under a microscope provides a unique identifier that can link a spent casing to a gun.

To be clear, microstamping deals with the cartridge casings that hold bullets before they’re fired, not the actual bullets. In most models of guns, the casings are ejected after they’re fired.

Microstamping provides order to a process that already happens when a gun fires. Standard firing pins leave their own patterns — known as toolmarks — on spent casings. But connecting markings on spent casings to the gun that fired them requires access to the weapon itself.

“All you’re doing in microstamping is organizing those in a way that’s easily recognizable,” said Joshua Horwitz, co-director of Johns Hopkins University’s Center for Gun Violence Solutions. “So instead of having random toolmarks, you’re organizing toolmarks in a way that gives you letters, numbers, and geometric coding.”