Surface metrology is commonly used to characterize functional engineering surfaces. The technologies developed offer opportunities to improve forensic toolmark identification. In 2009, a report by the National Academies called into question, amongst others, the objectivity of visual toolmark identification by firearms examiners. The National Academies recommended development of objective toolmark identification criteria and characterization of error rates. The National Institute of Standards and Technology (NIST) uses its experience in surface metrology to develop objective identification criteria, measurement methods, and reference artefacts. Objectivity is improved through measurement of areal surface topography and application of unambiguous surface similarity metrics, such as the maximum value (ACCFMAX) of the areal cross correlation function. Case studies were performed on consecutively manufactured tools, such as gun barrels and breechfaces, to demonstrate that even in this worst case scenario, all the tested tools imparted unique surface topographies that were identifiable. These studies provide scientific support for toolmark evidence admissibility in criminal court cases.
Citation: Journal of Physics: Conference Series
Pub Type: Journals
Striated Toolmarks, Impression Toolmarks, Areal Cross Correlation Function