A national registry to help solve gun crimes is in the works and it has already helped find a link to the shooting death of a police officer. FOX's Joy Piazza calls the shots with "Bullet Points": I'm Joy Piazza. A new tool for solving crimes by firing weapons involved in criminal activity. That's what the Phoenix police department is doing, connecting with a national database. Jessica Ellefritz is with Phoenix P.D. and says firing a confiscated weapon can help find its criminal history: (Ellefritz) "And its very similar to like a fingerprint, there are certain tool marks left behind on a casing when a gun is fired." High definition photos are taken of markings on the casings back at the lab and entered into the National Integrated Ballistic Information Network, NIBIN for short and compared to casings collected in other crimes: (Ellefritz) "At any given time there's a firearm sitting on a shelf in the police impound that could be the murder weapon from another homicide. And unless we test fire that and have those casings as a sample. We may never know that that gun was involved in a homicide." Phoenix police say their most notable cracked case, a shooting in 2013 linked to the shooting death of an officer across the country. And those are your Bullet Points! I'm Joy Piazza, FOX News!