NASHVILLE, Tenn. (WKRN) – Inside Metro Nashville Police’s Crime Lab there is a special section that takes the evidence left behind at shooting scenes and works to find connections in Nashville and other states.
“As a bullet is fired through a barrel it takes on what we call a mechanical fingerprint of that particular firearm,” Forensic Scientist Supervisor of Firearms and Tool Mark Identification unit Don Carman explained. “That’s unique for each particular fire arms.”
Analyzing those mechanical fingerprints and other aspects of firearms is commonly called ballistics. Carman is a world renowned ballistics expert.
At every crime scene involving a gun, officers collect all the evidence left behind by the gun, and when possible, the gun itself for testing.
“If we have a suspect gun we can test fire it in our laboratory and also identify the particular cartridge cases found at the crime scene,” Carman said. “Our model is we want to get timeliness of these shootings so it is a team effort.”
He continued, “It actually starts with the citizens of Nashville making that 911 call of shots heard or what they have seen.”
Carman told News 2 that is so important because often shooters will start by shooting at property, like abandoned homes or into cars as target practice.
If officers can collect the evidence when it is just a property crime, the hope is the crime lab can get information to detectives to help them find the shooter before they shoot someone.
“We find that there are a number of people who carry guns, but a much smaller group who actually fire weapons,” he said. “We used to call them active shooters, but now because of the times, we call them trigger pullers.”
The information from the evidence collected is analyzed and then entered to the National Integrated Ballistic Information Network (NIBIN).
Any gun or bullet tied to a criminal act or collected from a criminal suspect is entered into the system and then can be compared to all other bullet evidence entered into NIBIN.
It works a lot like the Integrated Automated Fingerprint Identification System (IAFIS) and the Combined DNA Index System (CODIS).
Both systems have been used to link crimes nationwide and close cold cases.
Metro’s crime lab has had more than 150 hits since May 2015 when the lab started using NIBIN.
Carman said that is a high number compared to other crime labs including the TBI’s lab, which also uses NIBIN.
“We are just one prong of this model,” Carman said.” We don’t know anything about the suspect we just analyze the evidence, the detectives then use it to investigate.”
Detectives are able to look for connections between shootings. It could be a group of people who are related, or the locations of the shootings has a connection and in some cases the suspect caught with the gun is tied to the other shootings connected to the weapon.
Metro police said an important part of making the system work is neighbors reporting shootings as soon as they can.