- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
National Institute of Justice
The Research, Development, and Evaluation
Agency of the U.S. Department of Justice
AFTE Theory of Identification
Home > Bullet Comparison and Identification > Identification > AFTE Theory of Identification
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Cutaway section of a handgun barrel
showing class and individual characteristics
In 1985, the AFTE Criteria for Identification Committee formalized the Theory of Identification as it Relates to Toolmarks. This theory articulates three principles that provide the conceptual basis for comparing fired bullets (and other toolmarked items). Class and individual characteristics provide the physical basis for the microscopic comparison.
For the purpose of this module, consider any use of the word “tool” as a reference to the rifled interior of a barrel and any use of the term “toolmark” as a reference to the impressions on a fired bullet.
The three principles of the AFTE Theory of Identification as it Relates to Toolmarks are:
- The theory of identification, as it pertains to toolmarks, enables opinions of common origin to be made when the unique surface contours of two toolmarks are in sufficient agreement.
- This sufficient agreement is related to the significant duplication
of random toolmarks as evidenced by the correspondence of a pattern
or combination of patterns of surface contours. Significance is determined
by the comparative examination of two or more sets of surface contour
patterns comprised of individual peaks, ridges, and furrows. Specifically,
the relative height or depth, width, curvature, and spatial relationship
of the individual peaks, ridges, and furrows within one set of surface
contours are defined and compared to the corresponding features in the
second set of surface contours. Agreement is significant when it exceeds
the best agreement demonstrated between toolmarks known to have been
produced by the same tool. The statement that sufficient agreement exists
between two toolmarks means that the likelihood another tool could have
made the mark is so remote as to be considered a practical impossibility.
- The current interpretation of individualization/identification is subjective in nature, founded on scientific principles and based on the examiner’s training and experience.
