Raman Spectroscopic Analysis of Organic Gunshot Residue Spanning a Range of Excitation Wavelengths

Ashley Hull, University at Albany, State University of New York

Abstract

Gunshot residue (GSR) is a type of trace evidence which can often be recovered at crime scenes. Organic gunshot residue (OGSR) is one of the two major subtypes of GSR. This study investigates the analysis of OGSR and aims to determine the optimum parameters at which to obtain Raman spectroscopic signals for OGSR particles at different excitation wavelengths. In this study a total of 5 different excitation wavelengths were utilized, namely 785 nm, 647 nm, 514 nm, 457 nm, and 406 nm, and 2 different ammunition types; 9mm and 0.38 in was examined for each wavelength. Each analysis sample was created such that OGSR particles were hand selected and placed upon a tape substrate. Each of these OGSR particles were cordoned off into a grid formation in order to ensure easy assignment of spectra to their respective particles. The determination of the optimum parameters for obtaining Raman spectra of OGSR at various excitation wavelengths aims to allow for ease of detection of OGSR using a Raman spectrometer regardless of laboratory capabilities or resources.