Interpretation of chemical data from glass analysis for forensic purposes

Abstract

The aims of evaluating forensic evidence are to provide a transparent, coherent, and unbiased opinion of the value of the evidence to fact‐finders. Measurements from glass evidence in a hit‐and‐run, for example, can help decide if a particular vehicle was involved in the accident. The evaluation involves the comparison of the physical, optical, and chemical properties of the glass recovered from the broken window with glass fragments suspected of originating from the window. A standard method (ASTM E2927‐16e1) describes a consensus‐based approach to sampling, sample preparation, quantitative analysis and “match” criterion for comparison of chemical properties. The result is a binary decision of either finding a difference in the elemental composition (exclusion) or a failure to exclude, based on elemental composition. This study demonstrates the utility of likelihood ratio (LR) calculations using novel datasets of glass samples of known manufacturing history. The LRs calculated from comparing glass manufactured at three different plants over relatively short periods (over 2‐6 weeks) range from very low values (LR ~ 10−3) when the glass are manufactured at different plants or manufactured weeks‐months apart in the same plant to very high values (LR ~ 103) when the glass samples are manufactured on the same day. Although the glass samples being compared may not originate from the same broken window source, they do exhibit chemical similarity within these lower and upper bounds and the LRs presented here, for the first time, closely correlate chemical relatedness to manufacturing history, specifically the time interval between production. The work presented here supports the use of the match criteria recommended within ASTM E2927‐16e1 and provides a data‐driven path forward to expand on the interpretation of glass using LRs.

Dimensionality reduction of multielement glass evidence to calculate likelihood ratios

“…These authors demonstrate that LRs can range from very low values (10 −3 ) for glass manufactured at different plants or manufactured weeks‐months apart in the same plant to very high values (10 3 ) when the glass samples are manufactured on the same day (even when the glass did not originate from the same “source”. These authors demonstrate that the calibrated LR s closely correlate to chemical relatedness because of manufacturing source and history, specifically the time interval between production 15 …”

“…Hoffman et al 7 then reported excellent performance of the MVK‐PAV approach when several operational laboratories were provided blind samples to compare, and LR s were calculated, based on the data collected in those laboratories. Finally, Akmeemana et al 15 report on the utility of calculating “calibrated” LR s using the MVK‐PAV approach for comparing glass that was manufactured at three different plants over relatively short periods (over 2–6 weeks). These authors demonstrate that LRs can range from very low values (10 −3 ) for glass manufactured at different plants or manufactured weeks‐months apart in the same plant to very high values (10 3 ) when the glass samples are manufactured on the same day (even when the glass did not originate from the same “source”.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…Akmeemana et al discussed the standard method ASTM E2927-16e , which is a consensus-based approach to sampling, sample preparation, quantitative analysis and “match” comparison of chemical properties. 127 Using glass from different manufacturers prepared days, weeks and months apart and analysing using LA-ICP-MS enabled the analytical data to be studied using chemometrics. Likelihood ratios were established that range between 10 −3 , where the glass comes from different manufacturers or from the same manufacturer months apart, to 10 3 where the glass samples are from the same manufacturer and prepared on the same day.…”

Chemical characterization of automobile windshield glass samples for major, minor, and trace elemental concentration determination by INAA and its comparison with ED-XRF and DC Arc AES in terms of analytical capabilities and possible applications for glass forensics

“…40 Comprehensive reviews and other literature are also available in recent years. 35,[41][42][43][44] This revealed that the elemental characterization of glass matrix is of high importance and high relevance even in today's scenario. Moreover, none of the reports were seen in the literature since early 90s, where NAA was used for elemental characterization of glass with potential importance to forensics.…”