Analysis of Retroreflective Glass Beads in Soil Samples for Forensic Investigations

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Description
Trace evidence is an essential component of forensic investigations. Anthropogenicmaterials such as fibers and glass have been well studied for use in forensic trace evidence, but the potential use of retroreflective beads found in soils for forensic investigations is largely

Trace evidence is an essential component of forensic investigations. Anthropogenicmaterials such as fibers and glass have been well studied for use in forensic trace evidence, but the potential use of retroreflective beads found in soils for forensic investigations is largely unexplored. Retroreflective glass beads are tiny spheres mixed into pavement markings to create reflective surfaces to reduce lane departure accidents. Retroreflective glass beads are a potentially new source of trace evidence for forensic investigations. Analysis of the spatial distribution and chemical compositions of retroreflective glass beads recovered from 17 soil samples were analyzed and compared to see if there are striking variations that can distinguish samples by source. Soil samples taken near marked roads showed significantly higher concentrations of glass beads, averaging from 0.18 bead/g of soil sample to 587 beads/g of soil, while soil samples taken near unmarked roads had average range of concentration of 0 bead/g of soil to 0.21 bead/g of soil. Retroreflective glass beads come from pavement markings, thus soil samples near marked roads are expected to have higher concentrations of glass beads. Analysis of spatial distribution of glass beads showed that as sample collection moved further from the road, concentration of glass beads decreased. ICP-MS results of elemental concentrations for each sample showed discriminative differences between samples, for most of the elements. An analysis of variance for elemental concentrations was conducted, and results showed statistically significant differences, beyond random chance alone for half of the elements analyzed. For forensic comparisons, a significant difference in even just one element is enough to conclude that the samples came from different sources. The elemental concentrations of glass beads collected from the same location, but of varying differences, was also analyzed. ANOVA results show significant differences for only one or two elements. A pair-wise t-test was conducted to determine which elements are most discriminative among all the samples. Rubidium was found to be the most discriminative, showing significant difference for 67% of the pairs. Beryllium, potassium, and manganese were also highly discriminative, showing significant difference for at least 50% of all the pairs.
Date Created
2023
Agent

Nuclear Forensics: An In-Depth Analysis of Capabilities, Improvements, and Limitations

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Beginning in the early 1990s, nuclear forensic science is a relatively young field that focuses on “re-establishing the history of nuclear material of unknown origin” (Mayer, et al. 2010, p. 1). Specifically, investigators compare these unknown materials, pre-detonation in this

Beginning in the early 1990s, nuclear forensic science is a relatively young field that focuses on “re-establishing the history of nuclear material of unknown origin” (Mayer, et al. 2010, p. 1). Specifically, investigators compare these unknown materials, pre-detonation in this case, based on their characteristics and process history (Mayer, et al. 2010, p. 1). In 2010, the Committee of Nuclear Forensics made ten recommendations on the procedures that could lead to improvement in investigation methods. In particular, this paper discusses Recommendation 6: “The nuclear forensics community should develop and adhere to standards and procedures that are rooted in the applicable underlying principles that have been recommended for modern forensic science, including calibration using reference standards; cross-comparison with other methods; inter-laboratory comparisons; and identification, propagation, and characterization of uncertainties'' (Committee of Nuclear Forensics, 2010, p. 11). The main objective of this paper is to compile a literature review to determine how this recommendation was followed, if at all, and produce a list of suggestions that could complement any effort towards the improvement of the field. Out of the methods recommended, that which has fostered the most growth has been cross-comparison. For example, the need for human supervision has decreased, which has decreased the need for human error (Reading, et al., 2017, p. 6013). However, areas that would benefit from development are increasing the number of disciplines in the field (Croudace, et al., 2016, p. 128). These conclusions provided the basis for improvements to other existing studies like DNA and fingerprinting.

Date Created
2021-12
Agent