Trace Evidence Section:


Vehicles, structures, tools, and other objects frequently have a protective/decorative coating applied that is generally described as paint. These coatings are a mixture of pigments and additives. Paint transfer can occur during the commission of a crime when two objects have contact. Paint examinations evaluate layer structure (sequence, relative thickness, color, texture, number and chemical composition) to a suspected source. A variety of microscopical and instrumental methods are used to compare samples.

Polymer examinations evaluate plastic, resin, or other manufactured materials that are chemically made up of long chains of molecules. The source, use, or manufacturer is not usually identifiable.  Methods of analysis are similar to those used for paint examinations.

Tape composition and construction can be compared with known sources. Tapes evaluated may include duct, vinyl, electrical, packaging, masking, and scotch tapes. Tape examinations may include visual, and microscopical evaluation of physical properties of the tape, as well as instrument analysis of the chemical composition of the tape. Evaluations for a physical fit can also be made using the torn end of tape compared to a suspect roll of tape, which is the only way of concluding they were once part of the same object. For example, if tape is used in the commission of a crime and a roll of tape is located in a suspect’s vehicle or house, a physical fit might indicate a relationship between the crime and tape recovered from the suspect’s property.