Differentiating circular from reciprocating saw marks in dismemberment cases
Description
Features on the cut surfaces of bones can be used in forensic anthropological analyses to provide information regarding saw characteristics in cases of dismemberment. For example, circular saws are reported to leave curved striae on the bone as opposed to the straight striae produced by reciprocating saws. However, accuracy and reliability rates have not been reported regarding practitioner ability in differentiating these two saw types. In this study, two observers with experience in saw mark analysis were asked to assess 43 photographs of cut bony specimens, molds, and incomplete cuts and determine whether they were made by a circular or reciprocating saw and report their confidence in their classification (scale 1-5).
Observer 1 correctly classified 80% of complete cuts in bone, 78.57% of incomplete cuts in bone, and 78.57% of molds, with an overall accuracy of 79.1%. Observer 2 correctly classified 66.7% of complete cuts in bone, 100% of incomplete cuts in bones, and 64.3% of molds, with an overall accuracy of 76.74%. A kappa of 0.62 indicates substantial observer agreement. These preliminary analyses were performed without any prior discussion of traits to use for classification. Understanding what features the observers used to classify the cuts (both correctly and incorrectly) will help us develop protocols for distinguishing circular from reciprocating saw cuts. Next, we plan to provide that protocol to a larger sample of observers with varied experience to better document accuracy and reliability rates and utility in forensic casework.
Citation Information
Eddy, Gloria; Cole, Stephanie; and Garvin, Heather, "Differentiating circular from reciprocating saw marks in dismemberment cases" (2026). Office of Research DMU Research Symposium. 103.
https://digitalcommons.dmu.edu/researchsymposium/2025rs/2025abstracts/103
Differentiating circular from reciprocating saw marks in dismemberment cases
Features on the cut surfaces of bones can be used in forensic anthropological analyses to provide information regarding saw characteristics in cases of dismemberment. For example, circular saws are reported to leave curved striae on the bone as opposed to the straight striae produced by reciprocating saws. However, accuracy and reliability rates have not been reported regarding practitioner ability in differentiating these two saw types. In this study, two observers with experience in saw mark analysis were asked to assess 43 photographs of cut bony specimens, molds, and incomplete cuts and determine whether they were made by a circular or reciprocating saw and report their confidence in their classification (scale 1-5).
Observer 1 correctly classified 80% of complete cuts in bone, 78.57% of incomplete cuts in bone, and 78.57% of molds, with an overall accuracy of 79.1%. Observer 2 correctly classified 66.7% of complete cuts in bone, 100% of incomplete cuts in bones, and 64.3% of molds, with an overall accuracy of 76.74%. A kappa of 0.62 indicates substantial observer agreement. These preliminary analyses were performed without any prior discussion of traits to use for classification. Understanding what features the observers used to classify the cuts (both correctly and incorrectly) will help us develop protocols for distinguishing circular from reciprocating saw cuts. Next, we plan to provide that protocol to a larger sample of observers with varied experience to better document accuracy and reliability rates and utility in forensic casework.
