Firearm Identification in the Forensic Science Laboratory

Introduction

• Authors: Robert M. Thompson, Christopher Chiles
• Publisher: National District Attorneys Association, supported by Bureau of Justice Assistance
• Purpose: Introduce prosecutors to the science of firearm and toolmark identification
• Key Concept: Modern forensic science and public expectations

History and Tools

• History: Over 100 years of forensic firearm and toolmark identification
• Primary Tool: Comparison microscope - unchanged in design for 80 years
• Technology: National Integrated Ballistic Information Network (NIBIN)

The Science of Firearm Identification

• Toolmarks: Created by harder tool surfaces on softer materials
• Class Characteristics: Basic identifying features (e.g., size, shape)
• Individual Characteristics: Unique imperfections on a tool’s surface
• Subclass Characteristics: Features shared by a limited number of tools
• Types of Toolmarks: Striated (scratches) and impressed (stamps)

Production of Firearm Toolmarks

• Firearm Types: Handguns (pistols, revolvers) and shoulder arms (rifles, shotguns)
• Ammunition Components: Cartridge, primer, bullet (projectile)
• Toolmarks on Fired Components: Impressions from firing pin, breech face, chamber

Examination Process and Trial Preparation

• Examination: Identifying toolmarks using comparison microscope
• Trial Preparation: Importance of pre-trial conferences between prosecutors and examiners
• Challenges: Understanding toolmark evidence and testing its admissibility in court

Firearm and Toolmark Identification in Courts

• Acceptance: Court acceptability under Frye/Daubert standards
• Scientific Method: Basis for identification processes
• Error Rates: Estimated at 1.0% for firearm evidence, 1.3% for toolmark evidence
• Standards and Peer Review: Importance of maintaining quality and accuracy

Automated Computer Search Technology

• IBIS/NIBIN: Digital mapping and database for firearm evidence
• Cold Hits: Identifications made through database searches

Glossary and Appendices

• References: Texts and journals for further reading
• Glossary: Key terms in firearm and toolmark identification

Conclusion

• Role of Examiners: Objectivity and ethical considerations in testimony
• Future Trends: Continued development in forensic technology and methods

This comprehensive overview provides a foundational understanding for those involved in the legal and forensic examination of firearm-related evidence, highlighting both the scientific and judicial aspects of firearm identification.