No Magic Bullet

Ballistic fingerprinting is the new magic crime-solving tool, and after the sniper attacks in the Washington area there is an understandable desire to do something. According to the Brady Campaign, recording the markings on bullets from all new guns "would have solved this crime (the sniper shootings) after the first shooting." It has also become an issue in the Pennsylvania gubernatorial campaign with Ed Rendell strongly supporting spending money on the program. Unfortunately, by draining resources away from other police activities and making it costly for law-abiding citizens to own guns, ballistic fingerprinting will more likely increase crime.

Despite frequent comparisons, ballistic fingerprints are not at all like human fingerprints or DNA, where the recording a child's fingerprints or DNA still allows for identification much later in life. Friction in gun barrels causes wear and changes the markings over time.

A better analogy is the tread on car tires. It is possible to take the tire tracks when left at the crime scene and match them with the criminal's car. But tires wear over time. If six months go by, the original print marks may not be much use.

Nor does it make much sense to put together a registry of tire treads on new tires on the off chance that a tire mark will be left at a crime. For example, brand new tires are essentially identical, leaving investigators with limited information on only the brand and model.

For bullets, the very friction that creates markings on bullets also creates wear. Except for the cheapest guns, the same models of brand new guns produce the same markings on bullets. And markings change slightly each time a gun is fired. For inexpensive guns with softer metal barrels, 50 or 100 rounds can make it very difficult to match bullets.

MORE PROBLEMS

Ballistic fingerprinting faces other difficulties. The process is defeated by replacing the gun's barrel. Scratching part of the inside of a barrel with a nail file would alter the bullet's path down the barrel and thus change the markings.

Even if a crime gun was not used much between when the ballistic fingerprint was originally recorded and the crime occurred, police must still be able to trace the gun from the original owner to the criminal.

Yet, only 12.1 percent of guns used in crime are obtained by the criminal through retail stores or pawn shops.

The sniper attacks in Washington are a good example of where the system works (bullets were matched fairly quickly to the weapon) and the attacker wanted police to know that the same person was committing the crime.

But that is not the same thing setting up a database on new sales and making matches after the gun has been used a lot.

So far only Maryland and New York have started recording the ballistic fingerprints of all new handguns sold. While Maryland's program technically started in January 2001, the cost of implementing the program made in unprofitable for gun makers to sell any handguns in the state for the first six months of the year. Only after the state temporarily agreed to pick up some of the costs, did sales proceed. The program cost $1.1 million to start and another $750,000 a year to run. New York's program began in March 2001 with start-up costs of $4.5 million. No estimates are available on the yearly cost for New York. The costs for dealers, gun makers, and for prospective gun owners are probably by far greater and were responsible for reducing handgun sales in both states.

So far the database on new sales is not encouraging. Not one violent crime has been solved in either New York or Maryland, and has only been used to identify two handguns stolen from a gun shop in Maryland.

PRACTICAL DIFFICULTIES

A recent study done by the state of California confirms the practical difficulties with ballistic fingerprinting. The report tested 790 pistols firing a total of 2,000 rounds, an average of just 2.5 shots per pistol. With cartridges from the same manufacturer, computer matching failed 38 percent of the time. When cartridges from different manufactures were compared, the failure rate rose to 62 percent.

This study does not even begin to address problems caused by wear.

Hence, in the real world, the failure rate can be expected to be much higher. The California report warned that "firearms that generate markings on cartridge casings can change with use and can also be readily altered by the users." Further, it warns that the problems of matching would soar dramatically if more guns were included in the sample. Its conclusion: "computer matching systems do not provide conclusive results . . . potential candidates (must) be manually reviewed."

Good intentions don't necessarily make good laws. What counts is whether the laws ultimately save lives.

Yet, "fingerprinting" all new guns will divert police resources from normal police work and make it more costly for law-abiding citizens to own guns. The result will be a more dangerous society.

John Lott, a resident scholar at the American Enterprise Institute, is the author of "More Guns, Less Crime" (University of Chicago Press, 2000).