SOME FORENSIC ASPECTS OF BALLISTIC IMAGING

ABSTRACT Analysis of ballistics evidence (spent cartridge casings and bullets) has been a staple of forensic criminal investigation for almost a century. Computer-assisted databases of images of ballistics evidence have been used since the mid-1980s to help search for potential matches between pieces of evidence. In this article, we draw on the 2008 National Research Council Report (1) Ballistic Imaging to assess the state of ballistic imaging technology. In particular, we discuss the feasibility of creating a national reference ballistic imaging database (RBID) from test-fires of all newly manufactured or imported firearms. A national RBID might aid in using crime scene ballistic evidence to generate investigative leads to a crime gun's point of sale. We conclude that a national RBID is not feasible at this time, primarily because existing imaging methodologies have insufficient discriminatory power. We also examine the emerging technology of microstamping for forensic identification purposes: etching a known identifier on firearm or ammunition parts so that they can be directly read and recovered from crime scene evidence. Microstamping could provide a stronger basis for identification based on ballistic evidence than the status quo, but substantial further research is needed to thoroughly assess its practical viability. Abstract Introduction I. Firearms Identification A. Toolmarks on Cartridge Casings B. Toolmarks on Bullets C. Uniqueness and Identification Issues II. Computer Images and Assessment of Databases A. Two-Dimensional Technology B. Three-Dimensional Technology C. Signature Analysis D. Scoring and Ranking E. Analysis III. Technical Feasibility of a National Reference Ballistic Image Database A. Performance Studies of IBIS Two-Dimensional Technology B. Panel's Assessment 1. De Kinder Data 2. NBIDE Data 3. NIST Study Overlap Metric C. Is a National RBID Feasible? IV. Microstamping: An Alternative Technology for Tracing to Point of Sale A. What is Microstamping? B. Origins of "Tagging" C. Legislation on Microstamping D. Microstamping of Firearm Parts E. Assessment of the Microstamping Option Conclusion INTRODUCTION For much of the twentieth century, the forensic science of firearms identification was an intensively individualized activity. A firearms examiner inspected ballistics evidence (spent cartridge cases and bullets) under a comparison microscope, formed a mental pattern of identifying marks and features, and tried to match that pattern against other exhibits. Establishing connections between different cases depended on the memory recall of the firearms examiner or being able to recognize features from photographs in open case files or postings on bulletin boards. (2) Hence, searching through large amounts of ballistic evidence and verifying a match was a labor-intensive and time-consuming task. Circumstances started to change rapidly in the late 1980s and 1990s as advances in compiling and searching computerized image databases were applied to forensic evidence analysis. The advent of the Federal Bureau of Investigation DRUGFIRE system (for cartridge cases) and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF)-funded BULLETPROOF system (for bullets) made the first significant breakthroughs, permitting individual law enforcement agencies to begin searching new ballistics evidence against large volumes of already-captured images and suggesting possible "hits." (3) The late-1990s formation of the National Integrated Ballistic Information Network (NIBIN), under ATF, broke down the previously formidable geographic barrier by linking the image databases across multiple agencies and permitting searches within regions of the country. (4) These advances in ballistic imaging technology allow images of bullets or casings to be cataloged, scored, and ranked. …