- 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
AFTE Theory of Identification
Home > Cartridge and Shotshell Examination > Identification Process > AFTE Theory of Identification
In 1985, the Criteria for Identification Committee formalized the AFTE Theory of Identification as it Relates to Toolmarks. The theory articulates three principles that provide the conceptual basis for comparing toolmarks for the purpose of identifying them as having a common source.
For the purpose of this module, consider any reference to the word “tool” in this section as a reference to the machined surfaces of the action and mechanism of a firearm. Any reference to the term “toolmark” refers to striated or impressed marks on a fired cartridge case or unfired cartridge cycled through the action of a firearm.
The three principles of the AFTE Theory of Identification as it Relates to Toolmarks:
- 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 contours. Agreement is significant when it exceeds the best agreement demonstrated between two toolmarks known to have been produced by different tools and is consistent with agreement demonstrated by 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.
