In large police agencies such as the Los Angeles Police Department (LAPD) or the NYPD, a huge number of firearms are confiscated from criminals each year. These guns must necessarily all be test-fired and the test-fired bullets and cartridge cases compared to bullets and cartridge
Shot pattern diameter 1" spread ~ 1 yard distance
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Shot pellet spread versus distance. A rule of thumb for investigative purposes only.
cases in unsolved cases. This would be an overwhelming task were it not for the advent of computer-based screening. In July 1992 the FBI developed a computer system called Drugfire for comparing the surfaces of fired bullets. The bureau also developed a system for examining the marks left on the bases of cartridge cases called Brass Catcher. In a classic example of bureaucratic duplication of effort, the ATF developed its own system, called Integrated Bullet Identification System (IBIS). Ironically, the two systems could not "talk" to each other because their software was incompatible. At the urging of groups such as the American Society of Crime Laboratory Directors, this problem was resolved, and the ATF system was universally adopted under the name National Integrated Bullet Identification Network (NIBIN). The system allows law-enforcement agencies access to databases in surrounding areas. Unfortunately it does not allow access to every police agency's database. At the NYPD, for example, the system does not currently allow access
Prior to the advent of databases of firearms component markings, it was generally believed that individual firearms were used by many different persons to commit crimes, especially in street gangs, but this theory could not be proved because law-enforcement agencies were unable to exchange firearms evidence in a systematic way. Following the introduction of databases for bullet rifling, cartridge case and firing pin impressions, and breech face marks, all that changed.
The FBI, for instance, found that one particular Berretta 9 mm pistol was responsible for two murders in Washington, D.C., a shooting in Baltimore, Maryland, and a holdup in Richmond, Virginia. Different individuals were responsible for each of the crimes, but all were members of the Crips street gang in Washington, D.C. As the months wore on, additional similar links between shooting crimes across wide areas and an individual firearm were found. The FBI was thus able to confirm that street gangs had weapons caches that were available to and used by members.
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