This article discusses the use of particle-correlated Raman spectroscopy (PCRS) to perform soil analysis in mock casework scenarios.
This study exploring the use of particle-correlated Raman spectroscopy (PCRS) to discriminate among soil minerals transferred onto mock-evidence items from different locations showed that area, diameter, perimeter, and volume are suitable metrics for PCRS analysis of soil and that PCRS is a powerful tool for mixture analysis and can demonstrate the discriminating potential of minerals for soil forensics. PCRS is a novel technique that combines microscopic analysis of particles with Raman identification and provides qualitative and quantitative information. When applied to soil minerals, this information includes identification and microscopic morphological characteristics (e.g. circularity, volume, area). Shoes and shovels were used to collect mock-evidence from three different geographical locations: an urban park, a rural woodland, and a suburban residential area. Known soil samples were collected from these locations to serve as reference samples for comparison. The soil adhering to mock-evidence items was collected and cleaned to isolate the mineral grains. The particles in the diameter range of 90-180μm were manually dispersed onto a Raman-inactive microscope slide and analyzed using PCRS. The results were compared to the reference sample results, and source consistency could be determined using mean and distribution statistical analysis. Adding heavy mineral separation to the sample preparation process allowed for a larger number of particles to increase features usable for match criteria. The mean and distribution, seen through single-factor ANOVA and Kruskal-Wallis tests, for these morphological features for multiple mineral classes were statistically indistinguishable between reference and mock-evidence samples.