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AFTE Theory of Identification

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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.

The three principles of the AFTE Theory of Identification as it Relates to Toolmarks: 

  1. 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.
  2. 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 can be considered a practical impossibility.
  3. The current interpretation of individualization/identification is subjective in nature, founded on scientific principles and based on the examiner’s training and experience.

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