Microscopic analysis of cut mark characteristics from chopping/hacking tools

Evaluating sharp force trauma (SFT) injuries to bone inflicted by a larger class of chopping/hacking tools (i.e., swords, axes, hatchets, machetes, and cleavers) is a growing area within the field of forensics. Previous studies have demonstrated promise regarding tool differentiation through the utilization of microscopic cut mark characteristics. However, this is an area that warrants additional investigation as there has yet to be a comprehensive study that incorporates the majority of these microscopic chopping/hacking cut mark characteristics into one analysis. The purpose of the current research was to analyze a large sample of microscopic cut mark characteristics derived from the current chopping/hacking literature to determine if differentiation of tool type could be made based on the microscopic cut mark characteristics. An additional goal of the current research is to develop standardization guidelines for the assessment of cut marks, focusing on a comprehensive suite of microscopic cut mark characteristics commonly observed in the existing literature. The skeletal sample for the current research was derived from a previous macroscopic cut mark characteristic experiment where trauma was inflicted to 20 partially fleshed domestic pig (Sus scrofa domesticus) limbs utilizing four chopping/hacking tools (i.e., axe, hatchet, machete, and cleaver) as well as a large carving knife for comparison. Cut marks were evaluated for 15 microscopic cut mark characteristics to assess statistical significance. Utilizing a chi-square analysis, nine of the 15 microscopic cut mark characteristics demonstrated statistically significant differences in relation to the tool utilized, indicating moderate to relatively strong effect sizes. For example, it should be possible to use a combination of microscopic cut mark characteristics to potentially indicate which chopping/hacking tool inflicted trauma when analyzing bones. In particular, examining the characteristics such as regularity of the cut mark edges along with the occurrence of uprising, fossae/depressions, and microscopic fractures can suggest or exclude tool class within forensic contexts.