ASTM E3328-25

1.1 This guide covers forensic examination of glass to determine one or more of the following: (1) if a particle is glass, (2) the compositional class and product type, (3) if exclusionary differences exist between two or more samples, and (4) the implications of the presence or absence of exclusionary differences between glass fragments.

1.2 This guide is for forensic science practitioners (FSPs) who conduct forensic glass analyses to aid in the identification, evaluation, selection, and application of test methods and procedures that can add value to an investigation. This guide describes an analytical scheme for glass fragments that is intended to advise and assist the FSP in the collection and interpretation of data resulting from these analyses. This document is not intended to describe methods in detail or to be a rigid scheme for the analysis and comparison of glass samples, but rather is intended as a guide to the strengths and limitations of each analytical method and as an overview of evaluation schemes. The detailed descriptions of procedures for many of the test methods are addressed in separate documents (refer to Test Methods E1967, E2330, E2926, and E2927).

1.3 This guide describes practices for collection of evidentiary glass for use by crime scene professionals.

1.4 This guide offers an overview of glass fracture analysis including reconstruction and physical fit. This is not a comprehensive guide on brittle fracture.

1.5 This standard is intended for use by competent forensic science practitioners with the requisite formal education, discipline-specific training (refer to Practice E2917), and demonstrated proficiency to perform forensic casework.

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 This guide is intended to assist the FSP in collecting glass evidence, then selecting and organizing an analytical scheme for identifying, analyzing, and comparing glass samples.

5.2 Glass fragments can be assessed for morphological (curvature, thickness, coatings, color, fluorescence), optical (refractive index), and chemical properties (elemental composition). Refer to Test Methods E1967, E2926, E2927, and E2330, which can be used to determine glass refractive index or elemental composition.

5.3 Glass fragment morphological properties, refractive index, and elemental analysis can be used to constrain the class or end-use of the glass.

5.4 For a glass comparison, glass fragments are assessed for physical fit of fracture surfaces and for similarities in morphological properties, refractive index, and elemental composition.

5.5 Fracture reconstruction can be used to reassemble the shape of the unbroken glass object.

5.6 Fracture analysis can be applied to assess type and direction of breaking force; approximate angle of incidence; point(s) of impact; and sequence of impact occurrence.