Iowa Department of Public Safety Division of Criminal Investigation

DNA Casework Section

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Trace Evidence

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TRACE EVIDENCE SECTION

The Trace Evidence Section of the DCI Crime Laboratory examines a wide variety of materials, from crime scenes, submitted as evidence. In the course of committing a crime small amounts of material may be transferred from one surface to another. Being able to establish a source for the transferred material may help connect the individuals involved to the crime scene. The Trace Evidence Section is set up for comparing the physical and chemical properties of questioned samples to the known samples.

The following is a list of the types of materials that can be encountered in a transfer of evidence and their possible sources:

Fibers - clothing, carpet, upholstery
Paint - vehicle, architectural, tools
Glass - vehicle, architectural, container
Soil - any source
Safe Insulation
Lubricants - petroleum and water based
Adhesives - tapes, glue
Plastics - vehicle trim, numerous other sources


Clothing from multiple locations


Material from two locations


Same material matched

Other examinations performed in the Trace Evidence Section:
Speedometer needle slap for determination of speed at the time of impact
Light bulb filaments to determine if "on" or "off" at the time of breakage
Duct tape comparisons
Determination of whether a match came from a particular matchbook
Rope and cordage comparisons
Toner comparisons from separate documents
Identification of unknown powders and liquids


Matchbook piece and match

Any questions regarding the collection or packaging of evidence may be forwarded to the DCI Crime Laboratory Trace Evidence Section at (515) 725-1500.

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