CHAPTER 6: The Use of Light in Forensic Glass Analysis

Glass is commonly retrieved in a wide range of crime types, including major and volume, both in the form of large, easy to analyse evidence items and more frequently as very small shards and fragments. Glass evidence has the ability to provide information not only to link individuals to broken glass items found at a crime scene but also to help establish what, when and how these were transferred. Light plays a fundamental role in obtaining this information, particularly source information, because the morphology, optical and chemical properties of glass can be characterised by different regions of both the visible and near visible electromagnetic spectrum. This chapter will provide an introduction to glass as evidence and how light is a partner to the forensic glass analyst in understanding the properties of glass and to answering questions posed by the criminal justice system. The limitations of techniques that use light at their foundation will also be discussed, because where light elucidates characteristics of glass that allow discrimination, it also highlights issues in the mass-produced nature of glass that must be acknowledged in forensic analysis.