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RESEARCH PRODUCT

Forensic comparison of PVC tape backings using time resolved LA-ICP-MS analysis

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Abstract Adhesive tapes are common tools for criminal acts such as the construction of improvised explosive devices. Hence, tape samples can be used as evidence to link a suspect to a scene of crime or different crime scenes to each other. A set of 87 black electrical tapes was the subject of a study evaluating a LA-ICP-MS method for the characterization of tape backings regarding their elemental composition in a forensic context. LA-ICP-MS is a powerful tool in forensic investigations due to fast, quasi nondestructive analysis of small samples and detection or determination of elements up to the ultra-trace range. In this study, the development of a semiquantitative LA-ICP-MS method for forensic tape examination using doped polymethacrylate as an “in-house” external calibration standard is presented. Semiquantitative data of Al, B, Ba, Bi, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sr, Ti, Tl, W, Y, Zn and Zr were obtained. These data were used to assess different match criteria with respect to their performance for the discrimination of tape samples originating from different rolls and association of tape samples from the same roll. A dataset of 87 PVC electrical tape samples from different rolls and a dataset of 24 samples (3 fragments from 8 sections) from each of three different rolls were analyzed to assess the discrimination and association potential of the method. The best compromises were found to be at 99.3% (100%) correct associations and 98.5% (97.5%) discrimination for symmetrical 5 (6) sigma match criteria using fixed relative standard deviations, which considered inter-day variations.