Reconsidering the Ballistic Imaging of Crime Bullets in Gun Law Enforcement Operations

Abstract Automated ballistics imaging and analysis systems, such as the integrated ballistic identification system (IBIS), have advanced gun law enforcement operations by allowing images of gun crime evidence to be rapidly compared to a large inventory of evidence collected from other crime scenes. After firearm examiners confirm candidate matches, detectives can use the information generated by the links among gun crimes to help solve their cases. Links between recovered cartridge casings represent the vast majority of ballistic matches made through IBIS. Unfortunately, the two-dimensional grayscale digital photography used by the original IBIS equipment was often not refined enough to suggest potential matches between often highly damaged bullets from separate crime scenes. Through the acquisition of three-dimensional measurements, the BulletTrax-3-D image acquisition technology was specifically designed to improve the ability of law enforcement agencies to make bullet matches through automated ballistic imaging and analysis. This study examines the impact of 3-D imaging technology on the productivity of the Boston Police Department's Ballistics Unit in making bullet matches. When directly compared with 2-D imaging technology, we find that the 3-D imaging technology acquired larger amounts of crime bullet evidence and was associated with a nearly fivefold increase in the cold bullet matches by the Ballistics Unit. Interviews with Boston Police detectives confirmed the considerable investigative value of the cold bullet matches.