Trace Materials is one of the most diverse forensic disciplines because it includes the analysis of many different materials that utilize a wide variety of laboratory techniques and analytical instrumentation.
The Trace Materials Unit identifies and compares specific types of materials that may be transferred from one source to another. A particular event or a series of events between two people and/or objects may result in the transfer of these trace materials. The analysis and comparison of these materials may link a subject to a victim or a crime scene.
Physical match examinations can be conducted by the Trace Materials Unit. For example, broken fragments may be reconstructed to show that they once formed part of the whole object.
Tape examinations are requested after the tape has been used to bind victims during a robbery, home invasion, kidnapping, or homicide. Using visual and analytical methods, it is possible to determine if the end of a piece of tape provides a definitive association to an individual source, roll of known tape.
Unknown chemicals, such as poisons, solvents, cleaners, tear gas, pepper spray, or other hazardous chemicals, can be examined and compared to known standards to determine the identity of the substance. This analysis could be significant in the investigation and prosecution of a crime.
Explosives can be examined after the item is rendered safe by the Bomb Squad. The Trace Materials Unit may examine items associated with the device. Common types of explosives that are analyzed are black powder, flash powder, smokeless powder, pyrotechnic mixtures, fireworks, and match heads.
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Fire debris analysis involves the determination of the presence or absence of ignitable liquid residues in an item obtained from a fire investigation. Fire debris samples must be packaged in metal paint cans, heat-sealable nylon bags, or glass jars. Improperly packaged samples will not be examined and may not be resubmitted for fire debris analysis.
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Plastic bags may be used in connection with criminal activity. The Trace Materials Unit looks at characteristics of the plastic bags formed during the commercial manufacturing process. The known and questioned plastic bags are examined noting class and individual characteristics observed.
Trace Materials Unit utilizes a variety of methods and techniques to analyze items of evidence. Instrumentation used includes gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS), infrared spectroscopy (IR), x-ray fluorescence spectrometry (XRF) and microscopy.
Currently, the Trace Materials Unit does not perform examinations on fibers, hair, wood, soil, paint, headlamps, or glass. These types of examinations may be sent to an outside laboratory for analysis if they qualify. The examination and comparison of paint and fiber cases requires that samples for comparison are submitted.