IBIS searched its database of ballistic images and matched shell case markings with those from an earlier shooting. Using this match, detectives were able to link the guns to the shooters and convict them. The New Orleans Police Department (NOPD) has had 60 hits from IBIS, and at least 10 cases have been linked. Like a fingerprint, each fired bullet and discharged cartridge case carries the firearm's unique bullet and cartridge case markings, sometimes called the ballistic signature. These markings are used to link recovered bullets and cartridge cases to the weapons that fire them. The NOPD compares every gun, cartridge case, and bullet received against all similar items in the database. As more evidence goes into the database, the number of hits grows. The NOPD also works with the Bureau of Alcohol, Tobacco, and Firearms as part of its ballistics tracking efforts. 3 photographs