Discrimination and classification among common items of evidence using particle combination profiles

Area of Science:

• Forensic Science
• Analytical Chemistry
• Materials Science

Background:

• Trace evidence analysis is crucial in forensic investigations.
• Very small particles (VSP) on common items are often overlooked.
• Established analytical techniques can be applied to VSP characterization.

Purpose of the Study:

• To determine the evidential value of very small particle (VSP) profiles.
• To assess the reliability of VSP analysis for linking physical evidence.
• To explore the potential of VSP as a novel trace evidence type.

Main Methods:

• Sampling of VSP from handguns, cell phones, drug packaging, and ski masks.
• Analysis using semi-automated scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDS).
• Application of statistical particle combination analysis for profile comparison.

Main Results:

• 84% of VSP specimens showed sufficient complexity for classification.
• Correct associations achieved for 93.5% of test specimens across evidence types.
• High accuracy in classification was observed with VSP numbers exceeding 125.

Conclusions:

• VSP are present on common evidence items and can be reliably recovered and analyzed.
• VSP profiles possess sufficient variety for classification using SEM/EDS and statistical methods.
• VSP analysis provides a quantitative approach to trace evidence, expanding its forensic utility.