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Ballistic evidence no longer a shot in the dark
FBI and ATF are building databases of 'gun prints' that can trace bullets back to the guns that fired them
By Gary Fields
The seven 9mm shell casings are magnified 10 times on the computer screen. Even at that size, they look identical, but they are not.
Using a specially designed microscope, a ballistics examiner compares the bullets. The backs of two of them have marks shaped like the state of Maine. That confirms what the computer has already found: the same gun fired both.
This scene at the Bureau of Alcohol, Tobacco and Firearms National Laboratory here is repeated dozens of times a day at more than 250 labs and law enforcement agencies in more than 40 states. Those labs and agencies are using new technology that in recent years has transformed ballistics-matching from a matter of luck into a science.
The technology has changed the way gun crimes are investigated and helped solved some perplexing cases, from street shootings in the USA to war atrocities in the Balkans.
Firearms examiners have always known that there are subtle differences in the marks every gun makes on the bullets it fires. Just as fingerprints have differences that can identify individuals, so, too, do the 220 million firearms in circulation across the country. When guns are fired, they pass along "gun prints" to bullets and cartridge casings.
But matching a single bullet found at a crime scene to the gun that fired it was backbreaking work, and success was often a matter of luck - until recently. A ballistics examiner trying to manually compare a 9mm bullet with records of thousands of other 9mm bullets "wouldn't live long enough to finish the search," says Benjamin Wilson, head of the firearms unit at the ATF National Lab.
Computers, and the databases being compiled by the ATF and the FBI have speeded that process greatly. Both agencies use computer systems that scan electronic images of thousands of bullets and the shell casings that were attached to them. Within minutes, the images can then /be matched with images of bullets and casings recovered in crimes. ,This system allows you to go through a tremendous amount of evidence in a short time," Wilson says.
Computerizing ballistics evidence also means that a single bullet can be used to catch a suspect. Until recently, ballistics tests were usually done only after police had a suspect and his weapon in hand. As they assembled evidence for a trial, police -would test-fire the gun and compare the bullets it fired with those found at a crime scene or extracted from a victim's body. When there was a match, they could use it as evidence of guilt
Now, a bullet recovered from a crime scene in one state can be compared - by computer - with bullets recovered from thousands of other crime scenes nearby and in other states. If there's a match, the bullets can be tied to a gun that was found or to a suspect caught or sighted at other crime scenes. The ballistics work is genuinely part of the investigation, not just the prosecution.
Not so long ago, an investigator would "get a gun test-fired to confirm his suspicions," says Paul Bolton, coordinator of the crime gun interdiction program for the International Association of Chiefs of Police. "The detective drove the forensics. Now it's the other way around. The detective can get a call now: 'Did you know this gun was used in a drive-by on the other side of town?"'
Making a match, solving a crime
1. Bullets, fragments, empty cartridge casings and test-fire samples from recovered guns are photographed with digital cameras, which convert them into computer images.
2. A computer compares the characteristics of a bullet or cartridge casing with thousands of other stored images. The best possible matches are pulled in minutes.
3. A trained ballistics examiner must compare the
evidence under a microscope and decide whether the
two images are a match.
The system's potential
The systems, have their limitations. There are 220 million firearms in the country, and, between them, the FBI and the ATF so far have only about 500,000 images on computer. The agencies hope that one day every gun used in a crime in America will be traceable to its owner using the distinctive "gun prints" it leaves on the ammunition it fires.
Examiners and police using the new technology have linked at least 5,700 guns to two or more crimes when no other evidence existed. Although that is only a fraction of the hundreds of thousands of gun crimes committed each year, officials see a day when the nations 30,000 law enforcement agencies will be connected by a national database of guns and ammunition.
The two ballistics computer systems in use - the FBI's Drugfire system and the ATF's Integrated Ballistics Imaging System - are not compatible. Only a few police departments - among them the Washington, D.C., department and several in the San Francisco Bay area - have access to both systems.
Today, the databases operate only on a regional level. For example, crime labs and police agencies in Delaware, Maryland, New Jersey, New York, Pennsylvania and the District of Columbia are linked with the ATF's Rockville lab.
But there is great potential for expanding the databases.
Manufacturers already keep the serial numbers of the guns they make, and they are working with the ATF and FBI to produce computer files of "gun prints" of all the new guns made in the USA. "We're just as interested as anybody else in keeping firearms out of the hands of the criminal element," says James Chambers, executive director of the Sporting Arms and Ammunition Manufacturers' Institute.
The work is in the test phase, but the hope is that eventually every new gun made in America will have prints on file, along with a serial number. "We want to be able to compare every piece of evidence with every known gun crime we have nationwide," says Frank Sauer, program coordinator for the ballistics exam system used by the FBI.
Already, many police departments can cite cases that would not have been solved were it not for the new ballistics technology. The technology "lets police agencies go back into open homicides and other cases and try again," says A.N. Moser, executive director of the National Sheriffs' Association.
Oakland investigators had little to go on in June 1997 when they tried to piece together the murder of Tommie Cain. Witnesses found the 22-year-old man inside his car. "The first people who got there said all he said was 'They were trying to rob me' and then he died," police Sgt. Derwin Longmire says. Investigators "weren't even certain where he'd been murdered. 'Mere were no leads, no witnesses to the shooting, nothing."
The next month, an Oakland patrol officer pulled over Jovan Reynolds, then 22, and Henry Bruce, then 20, for a traffic stop. Both had felony records; one was on parole and the other on probation. The officer found a .38-caliber revolver in the car, which meant immediate jail time for both men because neither was allowed to possess a weapon.
Because no other known crimes had been committed at the time the gun was found, officers took their time getting ballistics exams done of the gun. Several months later, when the gun was test-fired, police found that its bullet matched a bullet already in the imaging system, That slug had come from Cain's body. Armed with the information, Longmire questioned Reynolds and Bruce. It turned out Cain had run into the men while they were in the midst of a day-long robbery spree, Longmire says.
The case would probably still be open if not for the new technology, Longmire says. Reynolds and Bruce are now awaiting trial on murder charges. A third suspect has been identified but not charged.
One of the most startling examples of cases cracked by ballistics testing involved the International War Crimes Tribunal. ATF examiners confirmed in 1997 that 18 AK47 assault rifles were used to massacre 261 Croats in 1991 at a farm just side Vukovar in the former Yugoslavia. One person has already been linked to those assault rifles and convicted of war crimes. Other cases in the works.
The FBI began using Drugfire, developed by Mnemonic Systems in 1992 in response to the high murder rate in Washington. The ATF system, created by Forensic Technology, came the next year.
In both systems, bullets and car- [continued on page 20A]
Wilson: 'This system allows you to go through a tremendous amount of
evidence in a short time,' the ATF official says at the lab in Rockville, Md.
Following a bullet's path -right back to the gun
[Continued from 19A] tridge cases are photographed with a digital camera. Once the images are computerized, the systems measure microscopic imperfections and compare them with other bullets and shell casings in the system and find the most likely matches.
Needle in a haystack
"What our system does is pull the needle out of the haystack," says Robert Walsh, CEO of Forensic Technology's parent company. "It allows you to do something very fast. It's doing something you couldn't do before."
Firearms and ammunition can be so linked conclusively because of the marks guns leave on bullets and cartridge casings when they are fired. Inside a gun barrel, ridges direct and spin a bullet after it is fired. Those ridges cut grooves into the side of a bullet as it passes through the barrel. A gun's firing pin and breech also leave recognizable marks.
The result is a set of unique scratches, marks and other striations on the bullets and casings. Even two guns of the same model built by the same manufacturer will have different marks.
What the new technology does is find the images that are most similar to one another. Ultimately, human firearms examiners must confirm what the computer brings them, then testify at trial. They must convince jurors that the bullets match. The experts can be challenged under crossexamination, and defendants can bring in their own ballistics experts with different conclusions.
Martin Fackler, an expert on the impact bullets have on -the human body, says that, in the end, ballistics comes down to what the examiner thinks he or she sees.
"The question is, did this come from this gun at the exclusion of all other guns in the known universe?" Fackler says. "On one occasion, you can take 100 examiners and every one of them will say 'this is a match’ But sometimes you get two people who don't agree."
And that, says Bill Moffett, president of the National Association of Criminal Defense Lawyers, is his biggest objection to the technology. Juries might rely too heavily on technical results, he says, when in fact the results "are open to interpretation."
"There is no machine that you can put in facts and it comes out with an answer," he says. "All of them at some point rely on interpretation of a human being."
The ATF and FBI have been working for the past year to link their systems by computer. The two scan the images differently. As a result,. departments and labs with one system have been unable to search the databases of the other system.
In the absence of a computer link, departments and labs with the ATF system have been sending the actual bullets and cartridge cases to labs with the FBI system, and vice versa.
A second plan is to provide remote scanning systems to the 30,000 law enforcement agencies in the country so investigators can input images into the systems and do comparisons nationwide.
"Gun technology is in its infancy," says Sauer, one of the people in charge of making the ATF and FBI systems work together. "Me challenge on the technology is to take it beyond where it is today."