Comparison of screwdriver tips to the resultant toolmarks
Julie Ann Kidd · 2007
The subjective nature of correlating tools and toolmarks has been called into question since the 1993 Florida Supreme Court ruling in Daubert v Merrell Dow Pharmaceuticals, Inc. This has led to law enforcement agencies and officials placing an emphasis on developing objective techniques with known error rates to replace the traditional subjective comparisons. Additionally, if such objective techniques could be automated the heavy workloads currently faced by forensic examiners could be reduced. Development of a semi-automatic process that utilizes a three dimensional profilometer shows potential as a technique that may yield statistically verifiable results, removing the subjective nature currently inherent to toolmark evaluation, and be automated.;This work involves characterizing a number of consecutively manufactured tools with a scanning electron microscope (SEM) and comparing that tool to the resultant mark. By using software to analyze both the roughness of a tool and a toolmark---evaluated by SEM and profilometry---the two surfaces can be statistically compared and a correlation determined in a region of best fit. The project has sought to answer two distinct questions: Can a toolmark be related to a particular tool (and only that tool) on a statistical basis? Can a series of toolmarks be obtained and compared in an automated manner to yield a statistically valid match? Providing answers to these questions based upon quantitative techniques rather than subjective analysis removes the uncertainties raised by the Daubert decision. The methods employed have the potential for automation, thereby offering a means for decreasing examiner workload. Thus, successful completion of this project could lead to development of an automated system that produces statistically valid and verifiable results.