NCJ Number
88833
Date Published
1981
Length
39 pages
Annotation
This article discusses the physical and chemical properties of glass, variation in glass manufacture, glass fracture analysis, the forensic examination of glass, and the interpretation of glass fragment evidence.
Abstract
The greater uniformity of new glass and the attrition of older glass require the forensic analyst to reassess the population variation continuously (interpretive) and retain an ability to discriminate between commercial glasses (analytical). The older techniques of physical characterization are ensured a major role in glass comparison because of their simplicity, economy, and sensitivity; however, the significance of a correspondence in physical properties is diminished by decreasing population variation, so the forensic analyst must look for methods of characterization less affected by the manufacturer's quality control. Trace elemental analysis holds promise, although current techniques are limited by a lack of precision and the difficulties in interpretation that accompany it. Data analysis requires establishing the source of the trace elements and an assessment of the extent of their variation. Those chemical constituents that do not express individual variation can still be of use. With the uniformity of glass products comes an increased ability to determine the manufacturer and generic type of glass. Determinations of this nature become more important as variation diminishes. Physical characteristics common for some types of glass will be rare for others. Distinguishing these rare and common types of glass is crucial to interpretation. The merging of old and new methods is itself an important issue. There must be sensitivity to redundancy on one hand, but where the overlap in information is incomplete and resources will allow, all possible methods of differentiation should be pursued. Proper interpretation will only come from a complete understanding of the interrelationships among the various methods. Graphic and photographic illustrations are provided. (Author summary modified)