The Use of Light in the Analysis of Glass

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.