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Use of Infrared Imaging, a Robust Matching Engine, and Associated Algorithms to Enhance Identification of Both 2D and 3D Impressions

NCJ Number
Date Published
June 2009
44 pages
In examining the potential for infrared (IR) imaging to improve the utility of forensic firearm/tool-mark evidence, this project focused on the following evidence items: used cartridge cases, tool scrapes on metal, and footwear impressions.
Regarding used cartridge cases, the study found that due to the constancy of tool-mark features in IR images, and by eliminating the need to adjust lighting to highlight features, IR imaging and matching of cartridge cases required less time than current IBIS procedures. IR imaging produced a false positive rate of less than 0.005 percent. The results show a potential for significant savings in examiner time spent reviewing incorrect candidate matches in making conclusive identifications through conventional microscopy. IR imaging and matching of tool marks created by screwdrivers was also examined in this project. The technique developed produced a barcode representation of the tool mark that could be matched manually or automatically to barcodes of other marks. In a study of 100 tools (200 edges), the technique was effective in matching marks made by different people with the same tool. Regarding footwear impressions, two-dimensional IR imaging produced images of footwear impressions under dim light and total darkness. It also produced detailed images of athletic shoe-sole patterns without controlled lighting. Three-dimensional (3D) IR imaging produced dimensionally accurate 3D digital models of footwear and footwear impressions simply and rapidly. The primary advantage of IR imaging over visible light imaging for footwear evidence is its production of more consistent feature details under conditions of uncontrolled lighting. Feature contrast in IR images can generally be enhanced by air flow over the features, which differentially heats or cools portions of the features. This report proposes a three-part continuation of this project to include ammunition components, as well as further work in tool marks and footwear impressions. The IR imaging procedures used in each of the experiments are described in detail, along with the background of IR metrology. Extensive figures

Date Published: June 1, 2009