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Forensic Glass Analysis by LA-ICP-MS: Assessing the Feasibility of Correlating Windshield Composition and Supplier

NCJ Number
Abbegayle J. Dodds; Edward M. Pollock; Donald P. Land
Date Published
October 2010
125 pages
This study's goal was to provide forensic caseworkers with sufficient context regarding within-sample variation and population variation in the compositions of automotive windshields, so that the appropriate significance can be assigned to trace elemental data.
Prior to conducting this research, the research team validated the use of solution nebulization (SN) and laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS) for forensic casework in glass elemental analysis. The primary research determined that some, not all, windshield panes examined exhibited heterogeneity, and approximately half were composed of significantly different panes of glass. The study also found that the compositional variation of windshields from individual manufacturers was much smaller than that observed in the total population of automotive windshields. This finding suggests the potential for "fingerprinting" glass produced by specific manufacturers. Additional research is required in order to fully evaluate this potential. If this should prove to be a feasible means of correlating consumer glass products with their manufacturers, investigative information may be obtained from analyzing questioned fragments in the absence of reference samples. Using elemental data to provide investigators with putative sources of evidentiary glass fragments is an attractive possibility, since this is a common occurrence in hit-and-run offenses. The research collected and analyzed 50 automotive windshields representing 17 separate manufacturers and 1 unknown manufacturer. Researchers examined the within-pane variation of the interior and exterior panes of automotive windshields using a subset of 10 windshields, the total variation in elemental composition exhibited by all 50 windshields, as well as the variation observed within groups of manufacturers. The elemental data for all 50 windshields was organized into a Microsoft Access database. Qualitatively, the study examined the variation in glass production by analyzing quality-control samples collected directly from float glass manufacturers' stocks. 36 figures, 27 tables, and 61 references