Interpretation of Glass Evidence

The forensic examination of glass can provide information regarding the reconstruction of events, the type of glass involved in the case, and source commonality between a known and a questioned fragment. This chapter describes the main aspects of glass composition, manufacture, aftermarket distribution, transfer and persistence, and the scope of analytical methods used for its examination. The refractive index is the most common optical property measured during the forensic examination of glass. Elemental analysis is the most informative and discriminating step in glass comparisons. The way in which glass evidence is statistically evaluated is a forerunner of many ideas applied to other evidential material. The chapter shows how a case can be pre-assessed and how to sample the glass evidence depending on the case. It describes how examination results can be interpreted and finally examines how to evaluate the strength of evidence using both a two-stage approach and a continuous approach.