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Characterization and Comparison of Tape Evidence Using Elemental Profiling Methods and Chemometric Analyses

NCJ Number
253891
Date Published
Author(s)
Jose Almirali
Annotation
This is the final technical report on a research project that evaluated the performance of the conventional methods used in the forensic analysis of adhesive tapes and the recently developed elemental methods of analyzing adhesive tapes.
Abstract
The conventional methods of analyzing adhesive tapes are physical and microscopic examination, Fourier Transform Infrared Spectrophotometer (FTIR), Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC-MS), and Scanning Electron Microscopy using Energy Dispersive X-ray Spectrometry (SEM-EDS). The more recently developed elemental methods for the comparison of tapes are x-ray fluorescence (XRF), Laser Induced Breakdown Spectroscopy (LIBS), and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Two interlaboratory exercises were designed to study the performance of different analytical methods for the forensic analysis of electrical tapes. The exercises simulated forensic case scenarios in which known (K) samples were compared to questioned (Q) samples following the laboratory’s analytical scheme. The informing power, discrimination capabilities, classification potential, and certainty in the identification of elemental components increased with superior sensitivity and selectivity of the methods in the following order: SEM-EDS < LIBS < LA-ICP-MS. This study is a first effort in the standardization of the LA-ICP-MS and LIBS analytical and comparison methods. The results show good analytical agreement among the participating laboratories. Further developments in the standardization of methods for comparing spectrochemical data will improve the forensic utility of the methods described, Further research is required in comparing the results from different laboratories. A quantitative method of analysis would enable a comparison of the data from the labs, regardless of the instrumental parameters used. If a standardized method of analysis is used, ratios of elements would facilitate the comparison among laboratories for a single technique. 1 table, 6 figures, and 31 references
Date Created: October 27, 2019