2016
Michael Stocker
New Orleans, LA
A promising approach to improving the quality of tool mark data obtained in forensic laboratories is the measurement of the sample surface topography. Improvements in cost and capabilities of instruments for the optical measurement of surface topography have made this approach a viable alternative to the current practice of comparing sample images obtained using reflectance microscopy. A major advantage of measuring surface topography is that the measured data are less affected by variations in sample lighting conditions, focus, and sample reflectivity, thus facilitating the objective comparison of the actual tool marks. Instruments for measuring surface topography employ different measurement principles and have different performance characteristics. The presentation describes results of experiments conducted to improve understanding as to how these characteristics affect the ability to accurately discriminate same-source and different-source tool mark samples. This understanding is crucial to the development of measurement uncertainty in addition to measurement protocols and performance tests that yield consistent comparison results for different instruments, examiners, and laboratories.