A Comparative Analysis of Serrated and Non-Serrated Sharp Force Trauma to Bone
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Understanding patterns of trauma is important in order to assist in identifying and distinguishing between different weapon classes. Sharp force trauma is the second most common form of armed violence in the United States, however, research into establishing class characteristics that may help distinguish serrated from non-serrated blades in sparse in the forensic literature. This study addresses this gap in the literature.
Using two sets of 4.5 inch steak knives, one serrated and one non-serrated, 200 cuts were made to 100 porcine ribs. Subsequent examination of the trauma left behind in the bone was examined at several levels: macroscopic examination of the bone, microscopic examination of the bone, and microscopic examination of casts made of each cut. This study set out to answer whether or not it was possible to distinguish between these two classes of knives by examining the trauma that they left behind in the bone. In addition, it examines the unique nature of width, kerf shape, and presence or absence of striations.
Results indicate that it is possible to distinguish between serrated and non-serrated knives based on the characteristics of trauma left behind in bone. Descriptive statistics, as well as an ANOVA statistic were run on the width measurements, showing a highly significant difference between the two knife classes. Serrated widths all fell above .60mm (average width .910mm), while those cuts made from non-serrated blades falling below .50mm (average width .306). A Y-shaped kerf occurred in approximately 78% of serrated cut marks viewed macroscopically, and 82% when viewed microscopically. A Funnel-shaped kerf occurred in approximately 86% of all non-serrated cut marks when viewed macroscopically, and 87% when viewed microscopically. Striations appeared in 72% of serrated cut marks when viewed microscopically, and 76% when viewed from the casts of the cut mark. Additionally, striations only appeared 4% of the time in non-serrated cut marks when viewed from casts, but not at all when viewed microscopically.
Results of this study indicate that the identification of width, kerf shape, and presence of striations are useful for distinguishing between serrated and non-serrated knife classes. As such, these characteristics may be useful for assisting in the exclusion or inclusion of suspects and weapons in a forensic context.