The frustrating search for a serial sniper in the Washington region has renewed calls for a national ballistic fingerprint system that supporters say could quickly link bullets found at shooting scenes to a suspect.
Such a system would appear to offer a quick fix in cases such as the mysterious shooter who in the past two weeks has killed eight people and wounded two, apparently leaving behind little evidence except for scattered bullet fragments.
But some weapons experts say a program to "fingerprint" guns before they are sold - which is likely to be expensive and politically charged - also would be far from foolproof. The system could not account for stolen firearms, for instance, or for changes to the inside of a gun barrel that occur over time, they say.
"It's a tool, but not an end in itself," said Joseph Cominolli, a former firearms expert with the Syracuse, N.Y., Police Department who works as a gun safety consultant.
In Maryland, one of only two states that have launched a ballistic fingerprint database, police investigating the sniper shootings face one other hurdle - information in the Maryland system is limited to handguns sold in the state.
Rifles, like the kind of high-powered weapon the sniper is believed to have used, were exempted from the state law that created the database in 2000. The exemption was a way to appease lawmakers from rural areas, where hunting rifles are commonplace.
But Gov. Parris N. Glendening and Lt. Gov. Kathleen Kennedy Townsend said separately over the weekend that Maryland's law should be expanded to include some long-barreled and high-powered rifles.
In a voters forum Sunday at a Montgomery County synagogue, Townsend said she was exploring the issue with Col. David B. Mitchell, superintendent of the Maryland State Police, "because we want to make sure the police have in hand all the tools they need to make sure we're protecting our citizens and tracking down killers."
In an interview on the CBS news show Face the Nation, Glendening gave a blunter assessment, saying the Maryland law should cover assault and hunting weapons:
"If that were the case, and if that gun had been sold in Maryland, we would at least know where the gun was sold and to who it was sold. Quite candidly, I think that the ballistic [fingerprint] testing ought to be a national law because right now if you buy that gun in, let's say Texas, you could bring it up here and we wouldn't know."
Last week in New York - the other state with its own ballistic fingerprinting system - Democratic Sen. Charles E. Schumer said that the sniper shootings in suburban Maryland, Washington and Northern Virginia show that a national program is needed and he would introduce legislation to create one.
Gun-rights advocates, who have complained before that such a program would effectively create a national gun registry, warn that the shootings that have terrorized the Washington area are being used for political gain. The focus, they say, should be on catching a killer as quickly as possible.
"We feel that any effort to push a political agenda on the backs of these shootings is crass and reprehensible," said Andrew Arulanandam, a spokesman for the National Rifle Association, which has said little publicly in reaction to the sniper shootings.
Police can determine whether bullet fragments or casings found at a shooting scene match one another and whether they come from the same gun. In the current sniper case, law enforcement officials have used that information to link the separate shootings.
Ballistic fingerprinting goes a step further - linking a bullet or bullet fragment to a gun by its serial numbers and original sale information and, possibly, to a suspect.
To build Maryland's ballistic fingerprint database, gun retailers are required to provide police with a bullet casing from every new handgun before it is sold in the state. That fingerprint is created by the grooves and heat inside a gun barrel when it is fired, ballistics experts say.
"Every single [gun] barrel is different; it leaves different markings. It doesn't matter if it's made by the same company and it's the same type of firearm," said Cominolli, the Syracuse consultant.
Firearms examiners match bullets to guns first by firing a bullet from the gun they are trying to match, usually into a pool of water. The examiners then use a comparison microscope - a microscope with two lenses - to visually compare the markings on the bullets side by side.
"It's just like a fingerprint analysis," said Marshall Robinson, a retired Connecticut State Police ballistics expert who works as a consultant.
But experts also say that there is no guarantee that a bullet can be matched to a specific firearm, and just as traditional fingerprint evidence has faced new court challenges in recent years, ballistic fingerprinting also could be subjected to court scrutiny.
Bullets are made from a variety of metals, including lead, copper and steel. Many leave plating, or metal residue, in the gun barrels as they pass through. Sometimes this can cause slight changes inside the barrel, which over time changes the markings on the bullets that are fired, Robinson said.
"You have wear, use and abuse. When you fire a gun you're rubbing two metals together over high pressure and over high heat, and that's going to change things," he said.
Robinson was part of a team of ballistics experts that in 1997 analyzed the Remington 30.06 rifle that police believe was used in the assassination of the Rev. Martin Luther King Jr.
Despite 18 test firings and use of high-powered microscopes, the team could not match the rifle with the bullet that killed King, Robinson said. The 18 test bullets each had different types of markings.
"Every test bullet was different because it was going over plating created by the previous bullet," he said.
Robinson and others also pointed out that even when a gun can be tracked, it may not identify a suspect because it could have been stolen from the original owner.
'Not DNA; but it's close'
Supporters of a national ballistic fingerprint system acknowledge that the program would have flaws but say it would be a critical tool police.
"It's not perfect. It's not DNA. But it's close," said Eric Gorovitz, policy director for the Washington-based Coalition to Stop Gun Violence. "It's like fingerprints - they're unique markings that can be altered over time. ... But in most cases, they're not altered enough to destroy their usefulness.
Maryland's experience illustrates some of the limitations of ballistic fingerprinting. Since the program began in late 2000, the state has compiled information from about 17,000 casings, according to state police.
Authorities have used the information to make two matches to guns used in crimes, but no one has been charged.
Republican gubernatorial candidate Rep. Robert L. Ehrlich Jr. questioned last month whether the fingerprint program, which has cost more than $1 million, was working. As the sniper shootings have overshadowed the governor's race, and cast the political gun debate in a new light, Ehrlich's campaign has said only that the system should be expanded if it works.
Gorovitz said the sniper case has shown the system's potential: "The point is, knowing what we know - regardless of whether it would help solve this crime - we sure wish we had it."
Sun staff writer Howard Libit contributed to this article.