A ballistic fingerprint database is a computerized database of markings on bullet casings made by legally purchased guns. The idea is much the same as the fingerprint database AFIS or the DNA database CODIS, both of which house input known data to have to compare to unknowns found at crime scenes.
Both New York and Maryland have computerized ballistic fingerprint databases, both states have legal mandates that require all firearms manufacturers to provide, a spent cartridge and prepare ballistics images of the bullets and cartridge casings and provide the records so that the state’s law-enforcement agencies can access it, for every firearm legally sold; the law also requires that the name, address and Social Security number of the person purchasing the firearm be linked to the ballistics information.
The law, and the database, is based on the theory that that every gun marks shells and bullets in specific, stable, identifiable ways. The reason casings are used is because firearm that produce marks on cartridge cases are less subject to long-term wear. This theory, unfortunately, has not been scientifically proven. In fact, the markings left by a gun on a casing are not guaranteed to be the same over the long term and can be deliberately changed with simple tools such as a file or metal brush.
Another problem with the ballistic fingerprint database, as it stands, is that only new gun purchases are beholden to the law, meaning that the millions of already purchased guns cannot be traced via the database. Other concerns include the fact that less than 1% of legally guns sold will ever be used in a crime, guaranteeing wasted effort. Beyond that, nearly 90% of guns used in crimes change hands at least once after their initial purchase at a licensed dealer before being used in crimes; it has been estimated that nearly 40% of guns used by criminals are either stolen from their rightful owners or purchased on the black market.
There is also fault with the potential usefulness of such a database. California did some extensive testing to assess the accuracy of such a database and they found that when shell casings used with a particular gun came from the same manufacturer the computer failed to match the correct casing to its gun 38% of the time; when casings came from different manufacturers the failure rate was 62%. These false matches waste the time of ballistic examiners who are left ruling out matches made by the computer database. New York has had its database up and running since 2002 and has since entered data from over 200,000 new gun purchases and has spent approximately $1,000,000 a year on its system. By 2007 the system had not led to a single solved crime.
Fingerprint and DNA databases see their success from the fact that neither identifier is subject to change, a person is stuck with the DNA and fingerprints they are born with, but this is not the same for a gun and its parts. The parts of the gun that are responsible for marking a shell casing are the breech face, extractor, ejector, and firing pin, all of which can be purposefully altered with specific tools or all of which may change with time and normal wear. Although the idea of a ballistic database is appealing given the large amount of gun violence in the US, unfortunately the ease with which guns can be altered appears to throw a monkey wrench in the idea.