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Significance of Elemental Analysis from Trace Evidence

NCJ Number
Date Published
October 2012
70 pages
The objective of this research was to improve the scientific validity of the probative information that results from applying elemental analysis methods in the examination of trace evidence; glass analysis was the focus of the current research.
The study concluded that glass samples manufactured in different plants, or even at the same plant years apart, are clearly differentiated by elemental composition when micro X-ray fluorescence (m-XRF) methods or methods based on inductively coupled plasma (ICP) are used for analysis. Samples produced in the same plant over time intervals of weeks to months may also be differentiated. This level of differentiation can be used to add significance to an association and to assist in assigning recovered glass fragments to a source when selecting among several potential sources. Also, the inter-laboratory approach used in the research proved to be an efficient method for validating forensic methods and assess the significance of the evidence. It is recommended for other matrixes such as soil, paint, ink, and paper. The first part of the project coordinated a series of five inter-laboratory exercises that involved a large group of experienced examiners from several established operational forensic laboratories. They used mature forensic techniques and certified reference materials in order to demonstrate that the quality of the chemical information derived from a variety of analytical methods is good, regardless of the method used. The focus of the inter-laboratory exercises was on the characterization of glass evidence, and the soil matrix was also analyzed during one of the inter-laboratory trials. Until this project, there was no standardization of the m-XRF technique nor was there a systematic evaluation of the performance of m-XRF for forensic glass examination by a large number of users. 117 references

Date Published: October 1, 2012