Strengthening the evaluation and interpretation of glass evidence using statistical analysis of collection sets and databases of refractive index and elemental data (uXRF, ICP-MS and LA-ICP-MS)

As submitted by the proposer: The proposed development research aims to improve the interpretation of glass evidence using statistical analysis of existing collection sets of refractive index and elemental data (µXRF, ICP-MS, ICP-OES and LA-ICP-MS). This research will evaluate the collective knowledge derived from previously acquired glass datasets, surveys and databases. The FIU glass database (>700 different glass samples from known origin) generated through the TSWG-funded effort using both solution-digestion ICP-MS and LA-ICP-MS will be combined with other existing databases generated using ICP-MS methods (Sacramento County, Center of Forensic Sciences in Toronto and one large federal US laboratory that has indicated their willingness to collaborate with this effort). In addition, experienced µXRF users will also contribute their experience and databases in order to include the evaluation of µXRF data in the interpretation research. Finally, a representative from the Glass Association of North America (GANA) will also participate and provide useful background information and XRF data from glass manufacturing plants. The overall aim of this research is to evaluate the state-of-the-art interpretation guidelines (current SWGMAT draft interpretation scale and in review by OSAC committees) that are currently in use in some US laboratories and to converge on a common language through a consensus process by ICP and µXRF users. The proposed research will evaluate how the chemical information derived from ICP-MS and µXRF methods, when the data is collected and evaluated using the existing standardized methods (ASTM2330, ASTM2926 and ASTM2927) supports various statements of significance for specific case scenarios. Many studies have been conducted over the last three decades illustrating the discrimination power of elemental analysis for these types of evidence. Nonetheless, there is still lack of standardization and agreement among forensic examiners, including in match criteria selection in spite of the recently published ASTM methods. The proposed project will engage approximately 20 experienced trace examiners and a statistician that will participate in round-robin and discussion exercises over the course of two years. These group discussions will be designed with an aim to utilize the collective experience and knowledge base within the trace evidence community to address gaps in understanding of the significance of trace elemental profile matches and to converge on a common and consensus language that can be applied to describe the meaning of such associations for common glass case scenarios. It is expected that this approach will be expanded to include other types of trace evidence materials in the future and would therefore create a framework for the future efforts. This project contains a research and/or development component, as defined in applicable law. ca/ncf