The Trace Evidence team examines a wide variety of evidence for the purpose of identification and comparison.
As the term trace evidence implies, most evidence submitted to the unit is small or microscopic in nature. Several types of microscopes and scientific equipment are used to examine these items. Typical analytical requests include comparisons of questioned and known samples to determine if they could have a common origin or identification of a substance such as an ignitable liquid.
Comparisons involve analyzing and comparing questioned samples to known sources. An example of this would be glass from a broken window at a burglary scene to glass found in a suspect’s shoes. Comparisons also include evidence types such as fibers, paint, pressure sensitive adhesive tape and metals.
Identifications of substances may be necessary for investigative purposes or for criminal proceedings. These include ignitable liquid identification in fire debris, explosive identification in an explosive device or bank dye identification from bank security devices.
The Trace Unit also examines broken objects to determine whether or not they could have been joined at one time. This is called a physical fit. An example of this type of analysis is in hit and run cases in which vehicle parts have been left at a crime scene and an agency wants to know if they came from a suspect vehicle.
Services
- Paint (automotive and architectural)
- Glass
- Fibers and Cordage
- Tapes
- Building Materials
- Unknown Materials (General, Tampering)
- Physical Fit
- Ignitable Liquids
- Low Explosives
- Bank Dyes
Evidence Submission FAQs
You should send all the evidence to the lab you would normally submit to. If you are in the Madison Laboratory Service area, submit to the Madison Lab and they will forward the items that need Trace Unit work done to Milwaukee. If you ONLY need Trace evidence items examined, they should be submitted directly to the Milwaukee Laboratory.
Prior to submitting any tampering case, you should speak with a Forensic Case Manager or Chemistry Supervisor to ensure we can analyze the substance and the necessary items are submitted.
A small amount of liquid (about an ounce) should be packaged separately for submission to the Trace Unit. Any remaining gas should be removed, and the gas container then packaged for submission to the Identification unit or DNA.
No, we currently do not limit the number of items. If a large number of clothing items are collected, the clothing most likely to have been exposed to an ignitable liquid should be submitted (exterior clothing vs. undergarments). This will expedite the analysis and turn-around times.
Evidence Collection and Packaging FAQs
Yes, lined cans with a gray epoxy coating are suitable containers for fire debris. The coating does not interfere with the ignitable liquid testing. This applies ONLY to the gray epoxy coated cans (not the gold colored epoxy lined cans which have aromatic volatiles present). The lined cans also have the advantage of wet debris not rusting the can. Cans should be approximately 75 percent full when submitted to allow for proper analysis.
For known paint (auto or architectural), it is necessary to collect all layers down to the substrate (wood, metal, plastic etc.). Since known paints are generally not limited in amount available, it is recommended that you collect at least one or two nickel to quarter size pieces at a minimum.
For automobiles, known paint should be collected from all damaged panels near the area of damage since the chemical makeup of paint can be different on different body parts. This also applies to architectural paint. If damage in a forced entry occurs in a door jamb, collect known paint from the frame as well as the door.
Items of clothing that ONLY need to be examined for glass (no DNA needed) can be packaged together in a paper bag with the exception of shoes. Shoes need to be packaged separately. When removing clothing from a suspect, be sure to include the paper they undressed on. Generally, only exterior clothing is submitted (no undergarments).