Demonstrating the rationale for conclusions based on physical comparison carries more weight than a simple statement regarding wadding design. Therefore, availability of a reference standard is necessary for the identification of wadding materials. The reference standard may be from physical reference files maintained in the laboratory or from unfired ammunition seized during an investigation. Consistency of observable physical characteristics and their dimensions are key concerns addressed in the comparison.
If the wadding components are distorted or deformed, it may be necessary to obtain known standards by test firing to provide a better basis for comparison.
The following recommended procedure for examination of wadding material is consistent with the requirements of the Procedural Manual of the Association of Firearm and Tool Mark Examiners (AFTE).
The steps for this procedure are as follows:
- Perform preliminary procedures.
- Compare all physical characteristics of the evidence wadding component to the standards of similar manufacture and composition, including these:
- Measure diameter; use to determine gauge.
- Measure length.
- Design (number of petals, composition, shape).
- Determine composition.
- Determine number of petals – plastic wads only.
- Describe shape.
- Shot Size.
- Determine range of shot sizes as indicated by impressions on wadding material.
- Disassemble one unfired evidence shotshell for physical comparison of wadding materials, if required and available.
- Acquire fired standards for comparison, if wadding is deformed and distorted.
- Identify individual markings (these are unusual when found).
- Compare striated marks (if present) on wadding materials with standards fired from the evidence firearm.