Crime Scene Investigator Network Newsletter

Introduction
Paint is an important trace evidence material that can play a role in a crime investigation. It is usually associated with burglaries, automobile accidents, hit-and-run crimes, murder, and art forgeries. In the history of criminal investigation, many serious crimes have been successfully probed and solved using paint as evidence.

There are two types of paint that serve as evidence: household paint and vehicle paint. Such paint occurs as physical evidence in two forms: flakes or smears. Paint can be transferred during accidents at the point of impact. Flakes from a vehicle's surface may also be left at an accident scene or transferred to the clothing of the victim in an accident. Most paint specimens that are examined by forensic scientists are dry flakes with one or more layers.

Automotive finishes are the most complex in the paint industry. With advanced technology, more materials and intermediates are being used in the chemical industry. Hence, this presents a tremendous challenge in forensic paint examination.

Forensic examination of paint uses microscopy to determine color and layer structure and uses instrumental methods for compositional information. Advanced instrumentation in the field of forensic paint examination has provided new developments and has shown greater differentiation capabilities. However, the microscopic examination of paint flakes for color and other features is the most fundamental to characterize paint evidence. This is because the evidence can be readily assessed by such examinations.

The microscopic examination of the layer structure provides useful information such as color, tint, texture, metallic dispersion, layer order and thickness, inclusion between layers, and sanding striations on the primer layers resulting from refinishing procedures. The layer structure of paint flakes is considered significant because of the variations in car refinishing.

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