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Examination of Toolmarks From Sequentially Manufactured Tongue-and-Groove Pliers

NCJ Number
Journal of Forensic Sciences Volume: 25 Issue: 4 Dated: (October 1980) Pages: 796-809
F H Cassidy
Date Published
14 pages
The steps in the manufacturing process for Sears Craftsman tongue-and-groove pliers are reviewed, and several sequentially broached pliers as well as completely manufactured pliers' jaws are evaluated to ascertain if toolmarks from these pliers would be unique.
Tongue and groove pliers are often used in burglaries to twist off door knobs and thus gain entrance to a building. The study sought to determine if new, sequentially manufactured pliers would produce similar and indistinguishable toolmarks. Toolmarks from three sets of sequentially broached Craftsman pliers were examined and their manufacturing process analyzed. Findings from the analysis showed that no two consecutively broached pliers will produce similar striations. This diversity results from the manufacturing process. The individual metal in a particular pliers' jaw will have unique characteristics; surfaces of pliers are individualistic if surfaces are processed by tools such as grinders and broaches; the heat-treated scare and its removal are individualistic; the descaling process can impart different impressions on individual parts; and etching can cause differences and plating can cause striations. Microscopic examination of the toolmarks from the pliers thus verified that imperfections do produce individual characteristics, and specific manufacturing steps aid in causing the unique surface imperfections on each tool that are responsible for the individuality of its toolmarks. Photographs and nine references are provided.


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