BALLISTIC fingerprinting is one of the latest buzzwords in the fight against gun crime. Every time a gun fires a round it leaves a unique fingerprint of scratches and dents on the shell’s casing. Law enforcement agencies hope to use the unique signatures to match casings found at crime scenes to fingerprints of individual weapons held in a database.
New York and Maryland have laws requiring that all new guns be fingerprinted before they are sold. And police across the US use a ballistic fingerprinting system in which digital images of bullet casings found at crime scenes are entered into a national database in the hope they can later be matched to a weapon.
But the system is not foolproof. The more fingerprints that are added to a database the more difficult it is to make an accurate match. If the system is used to create fingerprints of new weapons, the problem can only grow as more weapons are sold. In California alone, 100,000 new handguns are sold each year.
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Researchers working for California’s Department of Justice fired shells from a particular weapon and asked the system to match the casing’s fingerprints against a database containing fingerprints from 792 cartridge casings fired by other weapons, including the one being tested. But the system failed to match identical rounds fired from the same gun 38 per cent of the time. And when the ammunition was made by different manufacturers, the failure rate rose to 62 per cent. The study also showed it takes only 5 minutes to change a gun’s fingerprint by defacing its firing pin or breach face.
To try and tackle the problem, California officials are evaluating technology developed by Nanovia, a company based in New Hampshire that specialises in etching microstructures on tiny silicon devices. Nanovia uses a pulsed UV laser to engrave a unique code of micrometre-scale letters on the firing pin head, the breach face, and inside the chamber where the bullet rests. When the gun is fired, the heat and pressure of the explosion makes the shell expand and this imprints the code on the casing. When police recover the casing, the code can be viewed under a microscope and linked to the make, model and serial number of the gun that fired it.
The process is extremely robust, says Todd Lizotte of Nanovia. The company says that its tests predict the embossing would be imprinted on the shell casing in all but six of every million firings. And it is virtually tamper-proof. “Even if someone finds one of the micro-codes and takes a file to it and wipes it away, there are still two others that will make the mark,” he says.
But gun manufacturers are “guarded” about the technology, according to Lizotte. “All of them say: ‘Go to the National Rifle Association and see if they would accept it.’ A lot of them are leery about adopting technology that could be construed as a negative within the gun community.”
