Article: Characterization of Aluminum Powders in IEDs, Part II
The Journal of Forensic Sciences recently published a new article co-authored by a Microtrace scientist. “Characterization and differentiation of aluminum powders used in improvised explosive devices – Part 2: Micromorphometric method refinement and preliminary statistical analysis” is co-authored by Microtrace Senior Research Microscopist Jack Hietpas, Ph.D. Part I, entitled “Proof of concept of the utility of particle micromorphometry” was published by the Journal of Forensic Sciences in October 2020. It explored the usefulness of automated particle micromorphometry for comparisons of Aluminum powders recovered from IEDs.
Part II refines the method explored in part I, using automated microscopy in combination with statistical techniques to provide source discrimination and investigative leads in source attribution of Aluminum powders in IEDs. The authors investigate 59 industrially and amateurly produced Al powder sources.
“Characterization and differentiation of aluminum powders used in improvised explosive devices. Part 2: Micromorphometric method refinement and preliminary statistical analysis.” Authors: Danica M. Ommen PhD, JenaMarie Baldaino MS, Christopher P. Saunders PhD, Jack Hietpas PhD, JoAnn Buscaglia PhD. Journal of Forensic Sciences, 19 November 2020
Aluminum (Al) powder is commonly encountered in improvised explosive devices (IEDs) as a metallic fuel due to its availability and low cost. Although available commercially in powder form, amateur bomb-makers also produce their own Al powder via simple methods found online. In order to provide investigative leads and forensic intelligence, it is important to evaluate not only the composition of homemade devices, but also to distinguish between the various forms of Al powder they contain. To achieve this goal, a method using automated microscopy in combination with statistical techniques has been demonstrated to have the potential to provide source discrimination and investigative leads in source attribution of Al powders in IEDs. The present research refined this method and investigated 59 industrially and amateurly produced Al powder sources with seven subsamples per source using two traditional linear discriminant analyses (LDA), one with a standard data split for training and testing, and another using leave-one-out cross-validation. Averaging the classification accuracies for the two LDA-based analyses, LDA has the ability to correctly classify 59.26%, 83.35%, and 80.69% of the samples based on their powder source, type, and production method, respectively. This classification accuracy represents a 3407%, 317%, and 61.38% increase in accuracy from random class assignment, respectively. Further, in most instances of incorrect data attribution to a particular source, the subsample has been misidentified with another sample of the same powder type or production method.