Ballistics Tests a Time Consuming Part of Ohio Shooting Probe
COLUMBUS, Ohio (AP) -- Though a sniper's bullet hits its target in an instant, it can take forensic experts days or weeks to match the projectile to its firearm or another bullet.
Microscopes will magnify the bullets and computer software can indicate similarities between digital images, but links must be verified by a human investigator comparing hundreds of tiny scratches and taking notes by hand.
It has been more than six weeks since a 62-year-old woman was shot and killed while a passenger in a car traveling on Interstate 270 on the city's south side. It is one of 18 shootings in the area over the last several months that has been linked by authorities.
A task force has connected seven recovered bullets from the shootings, and investigators have interviewed hundreds of people without identifying a suspect.
No weapons have been recovered from any of the shootings, and the task force won't say how many weapons it has tested from those who have been interviewed.
The time-consuming process of discerning a bullet's "fingerprint" sheds light on why the probe has dragged on. Experts say forensic testing of a bullet can take anywhere from a few hours to more than a week.
At the Columbus Police Crime Lab, which has handled all ballistics testing from the investigation, only one analyst is trained to compare bullets, said Jami St. Clair, the lab manager.
The analyst had to give up vacation time last year, and the testing of bullets in other cases has lagged because of the investigation, said Sgt. Brent Mull, a police spokesman.
"He's been working seven days week," St. Clair said. "I think he took Christmas off; that's about it."
Each bullet fired from a gun retains a pattern of scratches from imperfections in the gun's barrel. The unique patterns can be used to match bullets to one another or to a specific firearm.
Through a powerful microscope, the surface of a tiny, round bullet appears flat and furrowed -- like a metal washboard but more haphazard.
"It's probably the microscopic examination that takes the longest, but there's all kinds of time elements that are involved," St. Clair said. "The analyst has to take notes and visually examine it. He has to fire the suspected weapon in order to collect the bullet to compare it to an unknown. Reports have to be written and typed and signed."
The process begins well before the bullet reaches the lab. Two days after a house was shot on Dec. 15 -- one of the 18 shootings to be connected -- a technician on a ladder spent more than an hour carefully examining two bullet holes. Gusts of frigid air blew across the front yard as he used pliers to remove siding around one of the quarter-sized holes and later chipped at the wood beneath with a hammer and chisel.
Such deliberate work is required so the bullet isn't damaged further, a forensic investigator said.
"Whenever there's damage to the bullet, the damage can result in a loss of those individual characteristics. The more characteristics you have, the easier it is," said Ron Dye, a forensic scientist with the Ohio Bureau of Criminal Identification and Investigation who has helped confirm matches for the investigation.
Once a bullet arrives at a crime lab, analysts -- using their eyes or a relatively low-powered microscope -- look for blood, dirt or other evidence that could be swabbed for testing by a DNA specialist.
Analysts obtain test bullets by firing handguns into a 7-foot long metal tank of water, which slows the bullet while preventing further damage that would obscure scratches from the barrel.
Rifles fire bullets with greater force, so investigators use a 4-foot long steel box filled with quilting cotton for test firing.
Dye said investigators sometimes must fire several bullets to get a match comparable to one recovered from the crime scene.
Comparisons are done under a powerful microscope that allows two bullets to be viewed side by side. The forensic investigator uses sticky wax to attach the bullet to a crescent-shaped aluminum device, about 4 inches tall, which holds the bullet under the microscope lens. Tiny knobs and gears on the device allow the investigator to twist and turn the bullet so its scratches line up with those of its counterpart.
A dividing line separates the images of the bullets, but it can be configured so it appears to be an image of a single, continuous bullet.
"There are horizontal characteristics that tend to ignore the dividing line that gives you the illusion you are looking at one bullet instead of two," Dye said in an interview in the bureau's lab in London, west of Columbus.
A computer database, similar to what's used for fingerprints, allows authorities to compare digital images of bullets from across the country. But the evidence has to be examined side-by-side by a human to verify a match.
In 2003, the Columbus lab used the database, known as the National Integrated Ballistics Information Network, to compare bullets 1,965 times, which led to 86 matches, St. Clair said.