Comparative Evidence Unit:

Serial Number Restoration

Pursuant to the federal Gun Control Act of 1968, all firearms must bear a readily visible serial number on the frame or receiver. A serial number is a unique or non-repeating sequence of numbers and letters applied to a firearm by the manufacturer for the purposes of identification.

A serial number can be applied to firearms in different ways. The different applications are:

  1. Stamping

  2. Laser Etching

  3. Engraving

Some firearms have stamped metal plates molded into the frame or receiver; some have bar codes or QR codes in addition to the serial number. Contacting the specific firearms manufacturer in regard to the bar code or QR code is key in reading and understanding what the serial number is and if it has been obliterated in any way. Knowing the serial number allows a law enforcement agency to “track” the firearm from: its origin, different licensed or non-licensed sellers, the original owner of the firearm, and if the firearm was transferred from the owner to another buyer. This could aid in investigations when determining how a firearm made its way to a crime scene.

If a serial number on a firearm was obliterated, forensic laboratories have different methods to restore it. A variety of non-destructive and destructive methods are used to restore the serial number; they can be magnetic (non-destructive) or chemical etching (destructive). When a serial number is applied to a firearm by a manufacturer, it can alter the crystalline structure of the metal underneath it to a greater extent than the surrounding area. This allows the forensic laboratory to use these different restoration methods to re-visualize the serial number. Once the serial number is restored, it is documented and released in a report to the submitting agency.