Fire Scene Evidence Collection Guide

Fabric & Fibers

Single Fibers and Small Pieces of Fabric

Detailed Procedure:

Fibers are among the most commonly transferred trace evidence. They can be of considerable evidentiary value in linking individuals to crime scenes.

When possible, collect the entire item that the fiber is on and allow the laboratory to recover the fiber.

To collect single strands of questioned fiber and small pieces of fabric:

  1. Photograph the fiber and its substrate item, if any, in place.

  2. Wear new, unused, clean latex or nitrile gloves.

  3. If fibers can be seen, you should collect and secure the fiber at the scene, thus eliminating the chance the fiber may be lost when the item is moved (see step 4 for collection and packaging of fibers). Then, if the entire item can be transported, it should collected so that the laboratory can examine the item for more fibers or other trace evidence. Prepare appropriate packaging of sufficient size by labeling it with identifying information, including case number, date, exhibit number, a brief description, and your name. Carefully place the item in the container. Seal the container with evidence tape. Initial and date the tape.

  4. Use the following procedure to collect single fibers and small pieces of fabric off a substrate:

    1. Prepare a sheet of clean paper into an evidence or pharmacy fold. Post-it® notes are useful for collecting fibers as the fibers are lightly held by the adhesive, and after collecting the fibers, the Post-it note can be folded in half securing the fibers, and this can be placed in a prepared envelope. Prepare an envelope by labeling it with identifying information, including case number, date, exhibit number, a brief description, and your name.

    2. Using properly cleaned or disposable tweezers, carefully pick the fiber or small piece of fabric off the substrate. Take care not to crush or break the fiber when removing it.

    3. Place the recovered fiber on a clean sheet of paper or Post-it note, taking care not to crease the fiber in the fold. Place the folded paper or Post-it note into the labeled envelope.

    4. Seal the envelope with evidence tape. Initial and date the tape.

  5. Other ways of collecting questioned fibers (particularly if the fibers are not visible) from surfaces can be tape lifting or vacuuming.

    1. To tape-lift an item, using clear packing or book tape, make a tape lifter by wrapping the tape back on itself around the tape roll, sticky side out. Roll the tape on the item until you have covered the entire object. If the tape gets too full of debris, use a second piece of tape. Cut the tape off of the roll and lay it, sticky side down, on a clean piece of clear plastic or sheet protector. A sheet protector or plastic sheet can be placed in a properly labeled envelope or container.

    2. To vacuum an item, obtain a filter unit (these can be obtained from evidence collection suppliers) that attaches onto the nozzle of a vacuum hose. Proceed to vacuum the item and, when complete, preserve the filter (with the trace evidence on it) in an appropriate container, labeled with identifying information, including case number, date, exhibit number, a brief description, and your name. Seal the container with evidence tape. Initial and date the tape.

  6. Store the item in a secure location, such as a locked evidence van or your vehicle, until you are able to transport it to the laboratory. Please note that special storage may be required if the fabric or clothing may bear biological evidence, which should not be left in a hot car. Consult your laboratory for assistance.

If the fiber or small piece of fabric will also be examined for ignitable liquid residue, please consult the laboratory for the proper collection procedure. Items should not be air-dried or packaged in an air-permeable container if they will be examined for ignitable liquid residue.

Laboratory testing of questioned fibers:

Questioned fibers can be examined for class characteristics such as color, fiber type, cross-sectional shape, etc. Some fibers may indicate an end-use (eg.: carpet-type fibers, Kevlar). If a known piece of cloth, clothing or other object made of or containing fibers is submitted, the questioned fiber(s) can be compared to the known sample.

Source:

Crime Scene and Evidence Collection Handbook. Bureau of Alcohol, Tobacco, Firearms and Explosives, 2005

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