An Oct. 22 article about ballistic examinations being conducted in the Washington area sniper case misidentified the doctor who removed a thumbnail-size bullet fragment from the chest of a 13-year-old shooting victim. The fragment was removed by pediatric surgeon Martin Eichelberger. (Published 10/23/02)

When it hit him, the .223-caliber bullet was moving about 2,000 mph, and as it entered his body, it splintered. Shards of lead tore through his intestines and stomach, severed his pancreas and grazed one of his kidneys. The biggest fragment ricocheted upward and stopped in his chest.

As the unidentified man, shot Saturday night outside a Ponderosa restaurant in Ashland, Va., was rushed to a hospital in nearby Richmond, bullet fragments were scattered inside his torso like tiny pieces of confetti. That meant, as an emergency room nurse at the hospital put it, "his body was considered a crime scene."

So, as doctors worked to save the man's life, they knew that any bullet fragments they removed from his body would be important to law enforcement officials investigating the shooting.

Finally, on Sunday night, during the victim's second surgery, doctors removed a small chunk of lead, placed it in a specimen jar and gave it to law enforcement officials waiting at the hospital. The fragment was rushed to the national ballistics laboratory in Rockville run by the federal Bureau of Alcohol, Tobacco and Firearms. There, it was compared with bullets or fragments from a dozen shooting incidents attributed since Oct. 2 to a deadly sniper roaming the Washington region.

Yesterday afternoon, authorities announced what many people had suspected: The man outside the Ponderosa had been shot by the sniper.

The 12 previous shooting incidents -- in Montgomery, Prince George's, Spotsylvania, Prince William and Fairfax counties and in the District -- were highly similar. In each incident, a single rifle shot was fired from a distance. In one case, a bullet whizzed through a store, injuring no one. In the 11 others, nine people were slain and two wounded, all apparently at random, while going about ordinary activities.

With no solid witnesses, the bullets and fragments recovered from the victims and the store have composed the bulk of the investigators' hard evidence and allowed them to connect the shootings to the same rifle.

Including the Ashland case, ballistics matches were made in all but two of the attacks in which people have been shot. In the other cases, the bullets were too damaged to be accurately tested.

Those links have been provided not by law enforcement investigators pounding the pavement in search of the gunman, but by highly trained technicians in lab coats more accustomed to looking through a microscope's lens than a rifle's sights.

When magnified more than 100 times, unique scratches left on a bullet by the weapon it was fired from can be measured to the thousandths of an inch.

The inside of a gun barrels is lined with twisting grooves designed to put a spin on bullets, much like a quarterback spirals a football for accuracy. As the bullet squeezes through the barrel, the grooves leave unique marks in the lead, some of them invisible to the eye.

"Those minor scratches that are placed on the bullet as it travels down the barrel is what makes it uniquely identifiable to the weapon that fired it," said Susan Narveson, director of the forensics lab of the Phoenix Police Department and the president of the American Society of Crime Lab Directors.

Once the bullet fragment is turned over to a ballistics lab, technicians enter a digital image of the tiny markings into a computer database called the National Integrated Ballistic Information Network. The computer then spits out likely matches, which examiners further study under a microscope.

The ballistics evidence from the Ashland shooting was linked by lab technicians yesterday to the earlier sniper incidents in which bullets or fragments were recovered, the ATF said.

The technology, also called "ballistics fingerprinting," is used by the ATF and 160 crime laboratories across the country.

The technology has its detractors. The National Rifle Association, which has fought efforts to compile a national database of ballistics fingerprints from newly manufactured guns, has argued that grooves in the barrels of weapons change over time and can be easily altered.

But the ATF, which has used the computer database since 1993, lists "success stories" on its Web site detailing arrests that were made because of ballistics matches.

Lab analysts prefer to have the entire bullet, but a fragment as small as two square millimeters can be enough, said Pete Gagliardi, vice president of Forensic Technology Inc., the Montreal-based manufacturer of the Ballistic Imaging System.

But bullets can shatter into fragments smaller than that, leaving investigators without enough evidence for a match.

Investigators can also use shell casings, like the one found in the woods near a Bowie middle school where a 13-year-old boy was shot on Oct. 7, to link shootings.

When the trigger of a weapon is squeezed, a pointed firing pin strikes the base of the shell casing, igniting the propellant inside. The firing pin leaves a highly distinctive mark. Under microscopic examination, experts said, ballistics technicians can tell whether two or more shell casings were fired from the same weapon.

The casing, which usually has the manufacturer's name and the bullet's caliber etched on it, could also have an identifying mark left by the mechanism that ejects it from the weapon's chamber.

Law enforcement sources said yesterday that a laboratory examination concluded that a shell casing found at the scene of Saturday's shooting in Ashland matched a shell casing found near the Bowie school after the Oct. 7 shooting.

Given the importance of shell casings, bullet fragments and other types of physical evidence, the ATF started a program a few years ago designed to help doctors and nurses care for evidence as they treat crime victims.

"You take the bullet out and some doctors don't know what to do with it," said Jim Crandall, an ATF spokesman. In the past, he said, some doctors have thrown key evidence away, not realizing its importance.

That has not been the case with the doctors treating the sniper's victims.

As he operated on the boy shot outside the Bowie middle school, pediatric surgeon Kurt Newman was closing the boy's stomach when he realized that the largest piece of the bullet, a thumbnail-size fragment lodged in the boy's chest, could aid authorities. Doctors took X-rays to locate the fragment, and Newman made an incision to pull it out. The bullet fragment was placed in a cup and rushed outside the operating room where several law enforcement agents were waiting to take it to the ATF's lab.

At MCV Hospitals, where the Ashland shooting victim was in critical but stable condition yesterday, the emergency room is staffed by nurses who have been trained by homicide detectives to retrieve ballistics evidence, said Page M. Verlander, director of emergency nursing.

"They know how to handle a bullet," she said. "They know to wear a new set of gloves each time they handle a new piece of evidence."

Staff writers Avis Thomas-Lester and Tamara Jones contributed to this report.

Brian Depoy, a weapons expert, holds a .223-caliber bullet. The bullet is the same caliber as the ones reportedly fired in the sniper shootings.