Optimizing Particle-Correlated Raman Spectroscopy Methods for Forensic Soil Mineral Analysis

Soil evidence has the ability to provide investigative leads, as well as associate an unknown specimen from a shoe, tire tread, or shovel with a known. Although numerous cases have demonstrated the value of forensic soil analysis, criticisms (e.g., that it is subjective, labor-intensive, or time-consuming) have resulted in a considerable decline in its use in forensic investigations. The failure to collect and analyze soil evidence has created countless missed opportunities, and the criminal justice community is missing out on a valuable and powerful type of physical evidence that has been proved to help in the investigation and adjudication of cases. Consequently, there exists a need for a statistically supported, automated, and objective analytical method for soil analysis.

Particle-correlated Raman spectroscopy (PCRS), also known as particle-driven or morphologically directed Raman spectroscopy (MDRS), is a novel yet reliable analytical technique that can add significant value to the forensic examination of soil evidence. PCRS is capable of delivering particle-size distribution and microscopic morphological characteristics for the particles present within a soil sample, and at the same time PCRS provides secure mineral identification.

Brooke W. Kammrath presents research that focuses on the method optimization for soil mineral analysis with PCRS. The parameters for the chemical identification of minerals via Raman spectroscopy (laser wavelength, laser power, exposure time, magnification, and grating), the imaging of particles (the contrast/illumination method, magnification, and targeted morphological analysis), and dispersion of the particle mixtures were optimized using traditional comparative methods in addition to response surface modeling of a multilevel experimental design. The research presents the first steps in achieving the overall aim of developing a robust, automated, and objective analytical method for the analysis and comparison of soil minerals using PCRS.

About the presenter
Brooke Kammrath, Ph.D., is the Associate Director of the Henry C. Lee Institute of Forensic Science, and Associate Professor in the Forensic Science Department at the University of New Haven. She is also a Diplomate of the American Board of Criminalistics (ABC). Her research interests include uniting microscopy with spectroscopy, the identification and characterization of microscopic samples of forensic interest, the statistical analysis of trace, pattern and impression evidence, and investigations into the significance of physical evidence. Kammrath currently serves as President of the New York Microscopical Society (NYMS), and is on the Governing Board of the Eastern Analytical Symposium (EAS).