Independent Validation Test of Microscopic Saw Mark Analysis.

摘要

Microscopic saw mark analysis is a well published, generally accepted, and commonly used method. The strength of the method is that it is based on easily recognized qualitative and quantitative characteristics of a saw mark using standard laboratory equipment. Despite the methods attractiveness, it has not been independently validated, nor has the potential error rate been defined. Federal guidelines regarding admissibility of forensic testimony have become more rigorous in recent years, requiring a defined potential error rate. As a result, microscopic saw mark analysis fails to meet the requirements set forth by the Federal Rules of Evidence. The presented study is an independent validation test of microscopic saw mark analysis. The method, as published, was replicated without deviation and an ample sample size was generated for statistically sound analysis. Four morphologically different saws were used to make 58 partial and 58 complete saw marks in human femurs. The saw marks were examined independently by three doctoral level anthropologists using a digital microscope. Fifteen variables were documented for each saw mark. Descriptive analysis was performed using the Microsoft Excel 2007 statistical package. The data were further analyzed with classification trees and random forest classifiers grown with the rpart and randomForest libraries of the open source data analysis package R. Four variables were used in the classification tree and random forest classifier analyses: wall shape; floor shape; minimum kerf width; and average tooth hop.