Date of Graduation
Eberly College of Arts and Sciences
Forensic and Investigative Science
When two objects come into contact with one another, there is a potential for the transfer of material between those objects. The goal of this research was to develop statistical models to aid investigators in the reconstruction of a shooting incident. Specifically, the determination of the direction of fire from the angle of impact of the bullet was addressed by assessing the deformation of the bullet and the transfer of glass onto the bullet. Transfer of material to bullets is an underexploited area of trace evidence. Current research has mainly been observational and no attempt has been made to provide a quantitative measure to the results. Four aspects of bullet deformation after perforation of a glass target were studied during the research: (1) the shape of the bullet holes, (2) the side view of bullet deformation, (3) the frontal view of bullet deformation, and (4) the distribution of glass onto the bullets. A Ruger SR9 9mm pistol was used to fire 100 cartridges at individual glass samples at angles of 45°, 50°, 60°, 75°, and 90° using full metal jacket and lead round nose ammunition. The following methodologies were employed for image capture and analysis: (1) focus stacking was used to generate high-quality images of the frontal view of the bullet, (2) analysis of the bullet holes in the glass targets using HemoSpat, (3) analysis of bullet deformation and distribution of glass onto bullets using ImageJ. Regression modeling and principal component analysis were performed on the data. The research found that examining bullet holes in glass is not a viable method for determining angle of impact. It also found that the side view deformation of full metal jacket bullets can be used to distinguish between some impact angles, for example, 90° and 65°, but cannot be used for lead round nose bullets. Furthermore, the front view deformation and distribution of glass on full metal jacket bullets can be used to distinguish between some impact angles, for example, 75° and 50°, but cannot be used for lead round nose bullets.
Jeffreys II, Roger L., "Determining the Angle of Impact from the Analysis of Bullets Following Perforation with Glass" (2016). Graduate Theses, Dissertations, and Problem Reports. 7094.