James Wagster spends his day peering into empty shell casings, analyzing distinctive ridges and grooves that could link a fatal shooting in West Baltimore to a robbery on the East Side.

Daniel Van Gelder can dab the skin on someone's thumb and forefinger and not only tell if he has fired a gun recently but also show the exact location where a minute particle of gunshot residue landed.

He also can match an almost invisible white speck on the tip of a crushed bullet that has just passed through a man's head to latex paint on a wall, helping prove the man killed himself.

Wagster and Van Gelder are members of the Baltimore Police Department's increasingly high-tech crime lab, where new computers have accelerated the laborious task of testing everything from bullets to clothing fibers and have helped detectives search tens of thousands of case files in minutes.

"It doesn't pay for a criminal to do anything," said Edgar Koch, director of the laboratory division. "If he leaves anything behind, we are going to tag it."

These are the investigators the public doesn't see. They wear white lab coats instead of blue uniforms and stare into microscopes and at computer screens instead of racing to murder scenes. They get as excited about matching the ends of two pieces of duct tape -- which persuaded a man to confess to killing his wife last year -- as a street officer gets about making an arrest.

All qualified criminologists, they're holed up on the fifth floor of the police headquarters building downtown, lost in a maze of computers that can analyze anything from how much caffeine is mixed into a batch of heroin to a thread of lamb's wool on a car seat -- which nailed the killer of two women.

For detectives in the field, the additions to the lab mean shorter turnaround time for drug analyses and added ability to find links among cases that might not otherwise be discovered.

A $50,000 computer called "Drugfire," given in 1992 to the department by the federal government as part of a test program, is proving invaluable with years of data entered. It enables investigators to compare shell casings found at a shooting scene to any gun confiscated by police in the Baltimore-Washington region since 1992.

Without the computer, police would have to compare the weapon or cartridges to thousands of others stored in inventory -- a daunting, if not impossible, task unless a detective suspects a link in a particular case.

Detective Dennis Rafferty of the homicide unit said the computer has helped him learn motives and broaden the number of possible suspects in many cases. "I wouldn't have known they were linked if not for Drugfire," he said.

An example was the December shooting of David Lindsey Johnson, who was killed on a West Baltimore street corner.

Police recovered a 9 mm Argentine handgun, test-fired it and used Drugfire to examine the shell casing. In less than 10 minutes, the lab matched the cartridge to one found in a September break-in on East 31st Street, where police believe three armed men burst into the home of a suspected drug dealer to steal the profits of his illicit business.

Essential information

"This gun links the victim to a home invasion," Rafferty said. "I now know that my victim invades drug dealers' houses and takes their money. This is what probably got him killed."

Rafferty hasn't made an arrest in Johnson's slaying, but he called the information he learned from Drugfire essential to his investigation. Yet the lab technician who discovered the link had no idea how useful it was. To Wagster, it was simply case No. 8987, the 453rd time the computer system has made a match.

What Wagster does is place an empty shell casing under a microscope that projects an enlarged black and white image on a large computer screen, allowing a viewer to peer down the cylinder.

Enlarged, distinctive ridges or scarring -- made when the cartridge case recoils and hits the breach of the handgun -- become crevasses. Each gun leaves its impressions, or fingerprints, that can be compared with thousands on file. The computer shows the 10 best matches, which then must be compared individually.

The lab also has new computers that help technicians analyze drugs faster. Technicians process more than 23,000 drug cases each year, more than the six other drug labs in the state combined.

In another room, Van Gelder watches over a new $150,000 scanning electron microscope that tests for gunshot residue. Test results that used to take weeks -- and could easily be challenged in court -- now take 16 hours and yield more scientifically conclusive information.

Police used to spread hot wax on a suspect's hand, peel it off and test for nitrates. "It showed that you have either fired a gun or had been out spreading fertilizer on your grass," Van Gelder said.

With the new machine, a quick dab on the hand with a small disk is all it takes. The microscope analyzes the disk for barium, antimony and lead. Barium and antimony generally are found only in gunpowder.

'A lot of requests'

"This is evidence that has a lot of weight in solving cases," Van Gelder said. "With the number of shootings in Baltimore, we get a lot of requests for this test."

Van Gelder, who has spent nearly a quarter-century in the lab, says the computers -- such as the new $250,000 infrared spectrometer that can break down elements in paint -- help answer the "unanswerable" questions.

He used the equipment to solve the mystery of a man shot through the head. Matching paint from the bullet and wall showed a trajectory consistent with suicide.

"There was a witness who said he saw a known drug dealer in the area at the time of the shooting and wondered if it was an execution made to look like a suicide," Van Gelder said. "Without this machine, they would probably remain questions."

Pub Date: 4/21/97

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