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Toolmark Examination

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A flat-bladed tool (screwdriver)

A flat-bladed tool (screwdriver)

Courtesy of Jack Dillon

Toolmark identification is the microscopic comparison and potential identification of striated or impressed toolmarks as having been made by the same tool.

The foundation for this technique is based on the following principles:

  • A tool will bear unique microscopic characteristics due to the manufacturing processes it undergoes, as well as through use and abuse.
  • Tools will generally mark surfaces with which they come in contact with class and individual characteristics.
  • These class and individual characteristics are typically reproducible and identifiable with a particular tool.
Impressed toolmarks from a screwdriver tip

Impressed toolmarks from a screwdriver tip

Courtesy of Jack Dillon

Examiners should be aware and take into account the potential for the presence of subclass characteristics.

Toolmark comparison and identification are typically performed on the following types of evidence:

  • Test marks from an evidence tool compared to toolmarks on evidence items recovered from a crime scene to determine if the evidence tool marked the evidence item
  • Evidence toolmarks recovered from multiple crime scenes to determine if the scenes are related to a single tool

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