Date of Award

Summer 8-20-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department/Program

Forensic Science

Language

English

First Advisor

Linda Chiu Rourke

Second Reader

Peter Diaczuk

Third Advisor

Andrew J. Winter

Abstract

Fractured glass is often found at shooting scenes and can provide useful information for crime scene reconstruction. Mechanical glass fracture from a projectile impact can result in different types of fracture patterns. The degree of fracture depends on several factors including: type of glass, the thickness of the glass, curvature (if any), distance from the muzzle, contact angle, and type of projectile. Correlating impact energy to the degree of glass fracture can provide useful information regarding the muzzle-to-target distance for a particular firearm/ammunition combination. This research focuses on the projectile impact velocity of .177 steel BBs shot from a pneumatic air rifle. Double strength glass panes, of ⅛” thickness, were chosen due to its common use in residential properties. A Doppler radar system was used to measure the projectile velocity because it has the advantage of coupling Doppler processing with pulse radars to provide accurate velocity information with superior precision. The goal of this research is to characterize the relationship between impact energy and glass fracture pattern. The kinetic energy of the impact was calculated using impact velocity and projectile mass. The results of this study were divided into three categories based on the visible effects of the impact: BB ricochet with no visible damage to the glass (1.5J – 2.6J), BB ricochet with glass penetration and fracture (2.0J – 3.8J), and BB perforation with glass failure (2.9J – 4.6J). The results of our study can be used to develop future experiments using other types of firearms and ammunition to study glass fracture patterns.

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