An examination of electric chainsaw class characteristics in bone and the effects of thermal alteration
Young, Christina D.
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This study tested two hypotheses: (i) that the power of a chainsaw would affect the tool mark characteristics on bone that would allow for differentiation of a sub-class of characteristics for chainsaw tool marks; and (ii) that thermal alteration at three levels would not significantly obscure these class characteristics. Three electric chainsaws were used to create kerfs on 52 semi-fleshed white-tailed deer (Odocoileus virginianus) bones, which were used as an approximation for human remains. Bones were divided into 6 samples that were color coded to facilitate a blind study. The electric chainsaws used were: an 18-volt Ryobi® ONE + Lithium-Ion Cordless Chainsaw (low-powered); a 58-volt ECHO® Lithium-Ion Brushless Cordless Chainsaw (medium-powered); and a 120-volt Stihl MSE 220® Electric Chainsaw (high-powered). Each saw was assigned two color-coded samples, one as a control and the other for burning. All burned samples were divided into three sub-samples to facilitate low level burning, medium level burning, and high level burning. All kerf data were collected following Symes et al. (2010) and were observed macro- and microscopically (using a Meiji Techno EMZ-TR microscope). Data were analyzed using Row x Column (RxC) tests of independence, parametric single class analyses of variance, and non-parametric single class analyses of variance. A clear set of chainsaw class characteristics consistent with previous studies on power saw and chainsaw cut marks (Moore 2014; Symes 1992; Symes et al. 2010) was observed. Results supported the hypothesis that power classes of electric chainsaws have unique characteristics that allow for macro and microscopic visual identification of kerf characteristics. Primary differentiating kerf characteristics included: kerf width, kerf shape, false start to full break fracturing, entrance shaving, and exit chipping. Macroscopically identifying the low-powered chainsaw was successful for every kerf. Differentiating between the medium and high-powered chainsaw marks was more difficult but still successful in ≥ 88.2% of the kerfs. This research examines chainsaw power sub-class characteristics electric chainsaws and assessing the diagnostic viability of these characteristics when exposed to thermal alteration.