Forensic Glass Comparison: Background Information Used in Data Interpretation

• NCJ Number: 228196
• Author(s): Maureen C. Bottrell
• Date Published: April 2009
• Length: 21 pages
• Sale Source: US Dept of Justice Federal Bureau of Investigation
• Publication Format: Document (Online)
• Publication Type: Issue Overview
• Language: English
• Country: United States of America
• Note: From Forensic Science Communications, V 11, N 2, April 2009; downloaded September 1, 2009.

Annotation

This paper provides an overview of why glass and the nature of its constituent materials and manufacture make it an important item of evidence from a crime scene and when transferred to a suspect, followed by detailed descriptions of the forensic analysis and comparison of glass samples.

Abstract

Introductory information on modern glass manufacturing notes that although it is a highly automated process that produces glass with large-scale uniformity, minor variations in the properties of the resulting glass remain. Each of the raw materials used to produce glass contains impurities that are uncontrolled by the manufacturer and consequently vary in amount and composition over time. Thus, glass products have small but measurable variations in their chemical, optical, and physical properties both within and between production runs. A section on the "transfer and persistence" indicates that experimental studies have shown that glass fragments have been recovered from up to 4 meters away from a breaking glass object. Glass fragments can be transferred onto anything within this distance. Factors that control the number of glass fragments that can be transferred are discussed, as well as factors that determine whether the glass that is deposited on clothing persists to be available for recovery by a forensic examiner. The section on forensic glass analysis discusses the initial examinations, glass color and fluorescence, thickness, surface features, curvature, optical properties, immersion methods, Emmons double variation, an automated method for refractive index determination of glass fragments, density, and elemental analysis. Forensic methods described are scanning electron microscopy and X-ray fluorescence, neutron activation analysis, spark-source mass spectrometry, flameless atomic absorption spectrometry, and inductively coupled plasma methods. Remaining sections of the paper discuss interpretations/conclusions and the reporting of conclusions. 112 references