This "in-brief" report summarizes the objectives and features of the workshop on Applied Polarized Light Microscopy for Trace Evidence Examiners, which was part of the Impression, Pattern and Trace Evidence Symposium (IPTES) hosted by the Forensic Technology Center of Excellence on January 22-25, 2018, in Arlington, VA.
Polarized light microscopy (PLM) is a technique commonly used in forensic science in identifying and characterizing trace evidence found at crime scenes, such as fibers, hairs, paints, and glass fragments. PLM is useful for the quick screening of materials; and based on the properties observed using PLM, unknown samples can be easily identified and compared to other materials. In addition, microscopy can be paired with other types of instrumentation to aid in the identification and comparison processes. The 2-day course introduced participants to the theory and applications of PLM. Topics covered included proper microscope setup, refractive index measurement, basic optical crystallography, retardation and birefringence, extinction characteristics, and compensators. This summary of workshop material addresses microscope optics and setup, refractive index measurement, and crossed polars. Workshop instructors provide a listing of two resources.