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An Interlaboratory Study to Evaluate the Forensic Analysis and Interpretation of Glass Evidence



Katelyn Lambert, Shirly Montero, Anuradha Akmeemana, Ruthmara Corzo, Gwyneth Gordon, Emily Haase, Ping Jiang, Oriana Ovide, Katrin Prasch, Kahlee Redman, Thomas Scholz, Tatiana Trejos, Jodi Webb, Peter Weis, Wim Wiardia, Sharon Wilczek, Huifang Xie, Peter Zoon, Jose Almirall


The results of an interlaboratory exercise involving ten (10) operational and research laboratories employing laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and using a standard test method (ASTM E2927-16e1) for the forensic analysis and comparison of glass evidence are reported. The overall aims of the effort were to evaluate the performance of a newly reported calibration standard (CFGS2) for the quantitative analysis of simulated casework samples and to evaluate the use of a qualitative determination of the strength of association or non-association (as recommended by the ASTM E2927) and the use of a likelihood ratio (LR) as an objective and quantitative determination of the strength of any association found. Each laboratory determined an LR for the comparisons to report the significance of glass source comparisons for a set of glass samples of known origin. Both the ASTM E2927 match criterion and previously reported LR calculations were used to interpret the results of the comparisons reported by the 10 different laboratories. Two different background databases were used for the calculation of the LR to gauge the effect of the size and nature of the databases on the calculation of the LR. As expected, glass that originated from the same windowpane was found to be indistinguishable using the ASTM E2927 match criteria and result in a high LR value (suggesting strong support for an association between the glasses) and glass that originated from different vehicles are distinguished (resulting in a low LR, suggesting strong support for an exclusion). Glass samples that originated from different vehicles but that were the same make, model and year (or comparisons between the inner and outer pane of the same windshield) were found to exhibit chemical similarity that is sometimes reflected in a low LR. Good agreement among the laboratories was also reported for the analytical data collected using the standard test method of analysis for reference materials and the samples analyzed with relative standard deviations < 5 % RSDs among all labs participating in the study with few exceptions.
Forensic Chemistry


Lambert, K. , Montero, S. , Akmeemana, A. , Corzo, R. , Gordon, G. , Haase, E. , Jiang, P. , Ovide, O. , Prasch, K. , Redman, K. , Scholz, T. , Trejos, T. , Webb, J. , Weis, P. , Wiardia, W. , Wilczek, S. , Xie, H. , Zoon, P. and Almirall, J. (2021), An Interlaboratory Study to Evaluate the Forensic Analysis and Interpretation of Glass Evidence, Forensic Chemistry, [online], (Accessed June 6, 2023)
Created November 14, 2021, Updated November 29, 2022