This presentation will demonstrate the effectiveness of integrating 3D technology into the forensic firearms/toolmarks discipline and the decision analysis used for selecting samples for virtual comparison. In 2009, a report by the National Academy of Sciences (“Strengthening Forensic Science in the United States: A Path Forward”) called into question, amongst other issues, the objectivity of visual toolmark identification (note that firearms identification is considered to be a subset of toolmark identification). The National Academies recommended development of objective toolmark identification criteria and error rate estimates.
Currently in the forensic science community of toolmark identification, there are no objective standards for identification. In recent years, instruments have emerged with the capability to measure toolmark topographies and incorporate matching algorithms that have the potential to provide objective support for an examiner’s conclusion. In 2012, the FBI Laboratory’s Firearms/Toolmarks Unit (FTU) set forth with an approach aimed at addressing the recommendations identified in the NAS Report to evaluate the possibility of supplementing traditional light comparison microscopy with three-dimensional topographic measurement data. The FBI Laboratory had another goal: to determine the reliability of available algorithms to generate a score for match criteria and started acquiring instruments for this endeavor.
In 2014, the FBI Laboratory acquired the Cadre® Forensic TopMatch- GelSight instrument which uses the Bidirectional Reflectance Distribution Function to acquire 3D surface images and allows for side-by-side evaluation of surface topographies with a matching algorithm search capability for topography similarities. In October of 2017, the FTU completed its validation studies and established acceptable operating parameters for the Cadre® Forensic TopMatch- GelSight instrument and went live for casework to supplement light comparison microscopy for the examination of ammunition components. This presentation will cover highlights of the process, including the Standard Operating Procedures put in place, the laboratory workflow, selection of casework, blind verification incorporation, reexamination of casework using light microscopy and Daubert preparation.