AFTE Theory of Identification
Definition
The Association of Firearm and Tool Mark Examiners' standard (1992, revised 2011) for reporting tool-mark comparison conclusions as Identification, Inconclusive, or Elimination based on subjective assessment of individual characteristic correspondence.
- Framework origin
- Published by the Association of Firearm and Tool Mark Examiners in 1985, revised in 1992 and 2011.
- Applies to
- Firearms comparisons (bullet striations, cartridge case marks) and toolmark analysis (impressions and striations from any tool).
- Assessment basis
- Comparison of class characteristics (group features), subclass characteristics, and individual characteristics (tool-specific features) using stereo and comparison microscopes.
Common questions
What are the three conclusion categories in the AFTE Theory of Identification?+
The theory defines three admissible conclusions: Identification (a match is made), Inconclusive (the comparison is unclear and no definitive match or exclusion can be stated), and Elimination (the items are determined not to match). Examiners apply both class and individual feature criteria to reach one of these three conclusions.
How does an examiner apply the AFTE framework in practice?+
When comparing firearms or toolmarks like bullet striations or cartridge case impressions, the examiner assesses correspondence of class characteristics (features common to a group of tools), subclass characteristics, and individual characteristics (unique features specific to one tool). Based on the degree of match, the examiner assigns one of the three conclusion categories.
What makes a comparison 'inconclusive' under AFTE standards?+
An inconclusive conclusion means the examiner cannot determine a match or elimination with the required confidence level. This is a valid and admissible finding when the evidence does not provide sufficient individual characteristic correspondence to declare an identification or enough discrepancy to eliminate the source.
Related terms
- Class Characteristics
- Features deliberately or systematically imparted to a group of items by design or manufacture, such as the calibre of a bullet, the...
- Individual Characteristics
- Surface features on a fired bullet or cartridge case that arise from random or unique events (tool wear, corrosion, service damage) and...
- Comparison Microscope
- Two compound microscope bodies connected by an optical bridge that presents one half of each body's image in a single split eyepiece...
- PCAST 2016
- President's Council of Advisors on Science and Technology 2016 report 'Forensic Science in Criminal Courts', which assessed foundational validity of forensic disciplines...
- Asperity
- A microscopic surface protrusion on a tool's cutting edge; each asperity produces a groove in the substrate when the tool slides, contributing...
- BalliScan 3D
- Foster and Freeman's three-dimensional topographic bullet comparison instrument that maps striated surfaces using structured-light interferometry for both optical and digital comparison workflows.
- Black-Box Validation
- A study design where examiners are given unknown questioned-vs-known pairs and asked to match or exclude without feedback, allowing error rates to...
- Breech Face
- The forward surface of the bolt, slide, or breech block that seals the chamber and contacts the cartridge case head during firing....
- CMO Design
- Common Main Objective stereo microscope design using a single large objective with two off-axis optical channels passing through it. Allows better working...
- Congruent Matching Cells (CMC)
- An objective, measurement-based metric for cartridge-case comparison developed at NIST, quantifying the fraction of surface topography cells showing high correlation between questioned...
- Consecutive Matching Striae (CMS)
- A run of adjacent, individually corresponding striae observed across two bullets in the comparison microscope split field. The length of the longest...
- Ejector Mark
- A striated or impressed feature left on the cartridge case rim or base by the ejector pin at the moment of case...
Explained in these topics
- Bullet Striation Comparison and the Comparison MicroscopeThe 1985 framework published by the Association of Firearm and Toolmark Examiners that defines the three conclusion categories (identification, inconclusive, e...
- Cartridge-Case Markers: Firing Pin, Breech Face, Ejector and ExtractorThe 1985 AFTE framework that defines identification, inconclusive, and elimination as the three admissible conclusion categories for firearms and toolmark comp...
- Stereo Microscope and Comparison MicroscopeThe Association of Firearm and Tool Mark Examiners' standard (1992, revised 2011) for reporting tool-mark comparison conclusions as Identification, Inconclusiv...
- Tool Marks: Fundamentals, Striations and ImpressionsThe 1992 (revised 2011) AFTE framework defining class, subclass, and individual characteristics and the three available conclusion categories (identification,...