| Establishing a "Standard Method" for collecting, concentrating, and analyzing gunshot residue (GSR) evidence is a foundational step for establishing that an individual recently discharged a firearm. The systematic testing and analysis of various techniques for sample processing to establish a body of practices, and procedures for improving gunshot residue analysis is the goal of this research project. Gunshot residue analysis, in the past, has focused principally on detection of the residue. The evidentiary value of relating these detection results to an individual is governed by systematic quantitative GSR recovery and statistical data analysis. Only by establishing standard protocols for quantitative GSR sample collection and analysis can a reliable set of descriptive statistical data be created. By developing and testing standard methodologies for quantitative GSR evidence sampling and evaluation, this research will make a significant scientific contribution to advancing GSR evidence evaluation.;One of the most promising methods is the "Particle Method". This method uses the scanning electron microscope (SEM) in combination with energy dispersive x-ray spectroscopy (EDS). Many microscopic particles of GSR have unique shapes and elemental compositions. While this analytical method has proven valuable in detecting and identifying GSR particles, the lack of a standardized, validated sampling method often leads to uninterpretable or inconclusive results. Failure to establish a standard protocol for quantitative sample collection has seriously hampered using the "Particle Method" to establish a direct association between GSR particles and a shooter.;This research is an organized, systematic study of various collection, separation, and concentration techniques for quantitative measurement of the relative recovery rates of GSR particles. By following a standard protocol, the recovered amounts of GSR could provide a quantitative basis for establishing a scientific certainty in association. This is important fundamental research that will be of value in leading to further developments of GSR as physical evidence. The ultimate goal was to develop a standard method that would lead to a scientific basis for the association of an individual to a recent discharge, thereby assisting in the determination of guilt in firearm related cases.;This study established that through the use of a containment structure GSR particles could be deposited in a manner that allowed reliable recovery studies to be performed. It was also shown that computerized automated image analysis is a much improved method of counting particles for this class of research. Of the methods studied successfully for wide scale practical use, adhesive sticky lifts gave the highest recovery by more than two fold, but methods such as microvacuuming should not be rejected. |
