Correlation between saw blade width and kerf width

Abstract

Previous studies of saw marks have primarily focused on morphological characteristics and their utility in identifying saws suspected to have been utilized in cases of criminal dismemberment. The present study examined the extent to which metric analysis may be used to correlate saw blades measurements of kerf width. A sample of 56 partially defleshed white-tailed deer (Odocoileus virginianus) limbs were utilized as a proxy for human remains. The partial limbs were cut using a variety of commercially available saws, including 11 manual-powered saws and 5 mechanical-powered saws. A total of 500 false start kerfs (FSKs) were measured using digital calipers. Two experiments were performed, with the first test examining the kerf widths of false starts produced on specimens that were restrained using clamps, while the second test analyzed the kerf widths of false starts produced on minimally restrained specimens. Statistical analysis using Hierarchical Linear Modeling indicated a positive relationship between saw blade width (mm) and minimum kerf width (MKW), with the model estimating that MKWs would increase by 1.61 mm for every millimeter increase in blade width. Results from the models indicated that blade width (p<0.001) and the difference between mechanical- and manual-powered saws (p=0.029) were considered statistically significant. A comparison of MKWs produced using manual-powered saws on unrestrained and restrained bones suggests that restraint condition (p=0.009) is statistically significant. In comparisons of MKWs to blade widths, the average ratio for used saws was 2.7% greater than the average ratio for new saws. The mode of the ratios was approximately 1.4, supporting the general rule that MKW does not exceed 1.5 times saw blade width.