Evaluation of Staple Impressions in the Scanning Electron Microscope

Abstract

Use of the scanning electron microscope (SEM) for examination of tool marks, paricularly firing pin impressions of semi-automatic pistols, selected shotguns and rifles, is well documented. It was the intent of this investigation to apply SEM to staplers, in order to examine if the impressions on the shoe-ends of staples using a particular stapler possessed persisting defects with repeated tackings, and whether these defects can be used as “individual characteristics” in order to be able to identify the source of a staple on tacked papers from a list of eight staplers of different makes and models (Swingline® 747 and 27, ASCO® 40 and ACE® 102). The effects of pre-existing marks, which are usually existent as parallel striations on staples, and the different forms (100% round, 100% round with sharp points and chisel points) of staples on the resulting impression were examined by using different brands of staples (Swingline® standard No. S.F.-1, Swingline® R. W.-35, Bostitch® standard, and ACE® 2025).