Trace Evidence Section

August 30, 2020

Trace Evidence Analysis is based on Locard's Exchange Principle which states that whenever two objects come into contact there will be a transfer of materials from one item to the other. For example, when a crime is committed, material (or evidence) will be transferred between the suspect, victim, weapon, and/or crime scene. It is the discipline of Trace Evidence that examines much of the material from these exchanges.

The Trace Evidence Section at the Texas DPS Crime Laboratory includes the four sub-disciplines of (1) materials, (2) impressions, (3) gunshot primer residue, and (4) ignitable liquid residue. The materials sub-discipline is further divided into various specializations such as hairs, fibers, paint, glass, etc. The impressions sub-discipline examines the designs transferred to surfaces from shoes, tires, and/or fabrics. The gunshot primer residue sub-discipline examines microscopic particles associated with the discharge of a firearm to assist in investigations. The ignitable liquid residue sub-discipline performs analyses involving the detection of ignitable liquid residue in various types of burned and unburned materials.

The Trace Evidence Section analyzes evidence in cases of homicides, assaults, hit-and-runs, fire investigations, burglaries, etc. Instrumentation used in trace analyses can include gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, microspectrophotometry, and scanning electron microscopy. 

For a full list of analyses performed in the Trace Evidence Section along with information regarding the collection and preservation of trace evidence, and other considerations in this discipline, please refer to the Laboratory Customer Handbook (PDF) for specific information and instructions.