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Trace Evidence

We are responsible for the examination of small (trace) particles of evidence left behind during a crime such as hair, fiber, paint, glass, arson debris, gunshot residue, and other miscellaneous particles.

 
This kind of evidence is often present in violent crimes like rape, murder, robbery, arson, hit-and-run and kidnapping, as well as other crimes.
 
In the analysis of trace materials, we use several different instruments and methods which are described below.

Infrared Spectroscopy
Two different Perkin-Elmer Fourier Transform Infrared Spectrophotometers are used in the Trace Evidence Section.  The two instruments are used to analyze paints and other polymers, explosives, fibers, and unknown materials.

Inductively Coupled Plasma / Mass Spectroscopy
The technique known as GC/Mass Spec is used to identify arson accelerants and organic liquids.  Agilent Elan DRC-e Inductively Coupled Plasma/Mass Spectrometer is used with a Hewlett Packard 5970 Mass Selective Detector.

Atomic Absorption Spectroscopy
Perkin-Elmer SIMMA 6000 Atomic Absorption Spectrophotometer helps to detect components of primer residue in cases that involve the use of a gun.  The instrument also is used to detect lead in alcohol and arsenic in various samples.

Pyrolysis / Gas Chromatography
JHP-22 Curie Point Pyrolyzer attaches to a Hewlett Packard 5890 Series II Gas Chromatograph to analyze polymer samples.  Paints, tire rubbers, and other polymers are pyrolyzed and the resulting gas transferred to a gas chromatograph.

Scanning Electron Microscopy
A scanning electron microscope/energy dispersive x-ray system is used for high resolution and magnification imaging with enhanced depth of field.  The process results in a nondestructive analysis of gunshot residue particles, paints, metals, powders, and other trace materials.

X-Ray Fluorescence
Thermo-Electron Quan-X fluorescence system is used in the elemental analysis of glass, larger metal fragments, powders, and certain liquids.

Microspectrophotometry
Spectral differences in polymeric samples such as paints and fibers are measured with a Nanometrics NANO 100 UVIR Microspot Reflectometer.

X-Ray Diffraction
Inorganic components in samples with a crystal lattice structure are identified with a Rigaku D Max B X-Ray Diffractometer.  Samples may include —but are not limited to— arson materials, explosives, paints, powders, and pyrotechnics.

Microscopy
Stereomicroscopes, polarizing microscopes, and comparison microscopes are widely used in trace evidence analysis.


Trace Evidence Section:   Forensic Scientist Manager Timothy Suggs