State grant to help Allegheny County catch up on ballistics backlog
When a cartridge casing is magnified 80 times, the image looks like a big grooved disk, with crevices and craters like the surface of the moon.
Those microscopic dents and nicks act a bit like fingerprints. By comparing two casings or two bullets, an analyst can tell whether they were fired from the same gun, information that can be important for law enforcement in criminal investigations.
“If we have a casing that is from a robbery, and we tell police we linked it to a homicide from two years ago, then we know the gun is still in the area, we know it’s being used now,” Allegheny County Chief Medical Examiner Karl Williams said Tuesday. “It can help them put together the whole picture of what’s going on.”
The medical examiner’s crime lab handles the testing for all casings and bullets collected in Allegheny County — but it has a backlog of 1,700 untested casings, Dr. Williams said. Now, with $56,000 in funding from the state, Dr. Williams hopes to eliminate that backlog, which dates to about 2015.
Examining the untested casings will likely generate about 500 new matches to casings that have already been examined and entered into the National Integrated Ballistic Information Network, a national database with images of casings and bullets collected at crime scenes.
That’s 500 potential new leads for local law enforcement, which explains why Pittsburgh police helped the medical examiner’s office secure the state funding. The money allocated to the medical examiner’s office was part of a $250,000 grant given to Pittsburgh police last week in a statewide effort to reduce gun violence. City police plan to use the remaining funds to expand their gun violence reduction team.
“Everything is a collaboration with police,” Dr. Williams said.
The medical examiner’s portion of the money will be used to buy new cameras for the microscopes used in the testing, as well as to pay for overtime so staff can chip away at the backlog of casings. At the same time, the team will still examine new casings and return results to law enforcement within a few days, Dr. Williams said.
The process of checking for matches begins with a black box that sits on a tabletop in a laboratory. An analyst places a casing into the box, which uses software to create a 3D digital image of the casing.
The casing is the metal tube that holds the primer and powder. The bullet sits atop the casing; those components together are the cartridge.
The 3D image is entered into the NIBIN database, which checks the image against thousands of others entered across the region and returns a short list of potential matches within a couple of hours.
Then it’s up to a human to carefully compare the casing’s image to the potential matches. If a hit looks like a legitimate match, the analyst will pull the actual physical casings and examine both under a microscope.
On Tuesday, scientist Anita Lorenz examined two magnified images of casings on her computer monitor. These particular images came from casings fired from a gun that was found and turned in to police, she said.
When guns are recovered, crime lab staffers obtain casings and bullets by firing the guns into a 500-gallon tank of water that sits in the middle of their Strip District offices on Penn Avenue. Analysts can connect casings to casings and bullets to bullets but can only tie casings and bullets back to guns if the firearm has been recovered.
On her computer screen, Ms. Lorenz dragged the magnified images on top of each other.
At first, the grooves didn’t seem to line up.
“That could be because the gun is old, maybe there was some rust inside it,” Ms. Lorenz said. “But there are other areas you can look at.”
She scrolled to another part of the magnified image and suddenly the crevices perfectly aligned — showing the casings had been in the same weapon.
“Ultimately,” Dr. Williams said, “it comes down to people.”