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Shooting Distance Determination: Identifying Variables Affecting Lead Density on a Target

NCJ Number
254403
Date Published
Agencies
NIJ-Sponsored
Grant Number(s)
2016-DN-BX-0184
Annotation
This is the Final Summary Overview of the findings and methodology of a project with the goal of developing a statistical foundation that supports the established methods for determining the muzzle-to-target distance based on empirical research, so as to demonstrate quantitatively that the lead distribution on a target is directly related to the firing distance.
Abstract
One principal finding is that the lead extraction method with nitric acid is effective in extracting the elemental lead from the target, as well as lead salts. A second finding is that the limit of detection (LOD) for lead by atomic absorption spectroscopy (AAS) is lower than the LOD for the sodium rhodizonate test. This finding has implications for both lead-free and total-metal-jacket bullets. Even hollow points often have an aerodynamic polymer plug that covers the point of the bullet. If these trends continue, chemical analysis of targets may become more important in gunshot residue (GSR) analysis for shooting distance determinations. A third finding is that the ratio of lead density of the inner (1.0 cm-5 cm) to the outer (5 cm-19 cm) rings of the target does not provide better distance determination than the sum of the lead from 1.0 cm-7.5 cm. A fourth principal finding is that the differences in the data between analysts varied to a greater extent than the data collected by one analyst. Although the researchers advise that this project has not fully identified the factors that affect the lead deposition, the greater lead sensitivity of the AAS is a sufficient reason to continue examining analytical methods for determining shooting distances. Project design and methods are described. 2 figures and a listing of sources for the dissemination of project methods and results
Date Created: December 16, 2019