Hair

Detailed Procedure:

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

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To collect questioned hair:

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

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

3. If hairs can be seen, you should collect and secure the hair at the scene, thus eliminating the chance the hair may be lost when the item is moved (see step 5 for collection and packaging of hair). Then, if the entire item can be transported, it should collected so that the laboratory can examine the item for more hairs or other trace evidence.

4. Once the hair has been collected (see step 5), prepare appropriate packaging of sufficient size for the item 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.

5. To collect hairs from a substrate, use the following procedure:

   1. To collect visible hairs, use properly cleaned or disposable tweezers and carefully pick the hair off the substrate. Take care not to crush or break the hair when removing it. Place the recovered hair on a clean sheet of paper or Post-it® note (Post-it notes are useful for collecting hairs as the hairs are lightly held by the adhesive), taking care not to crease the hair in the fold. Place the folded paper into a properly labeled envelope (case number, date, exhibit number, a brief description, and your name).

   2. Other ways of collecting questioned hairs (particularly if the hairs are not visible) from surfaces can be by 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. The sheet protector or plastic sheet can be placed in a properly labeled envelope or container.

      2. To vacuum an item, obtain a filter unit (which 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 and properly labeled container.

6. Seal the container with evidence tape. Initial and date the tape.

7. 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.

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If an item 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.

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To collect known hair exemplars:

Head and pubic hairs are generally the only human hairs that can be compared to known hairs. However, beard hairs may be suitable for comparison (check with your laboratory). When collecting known hairs for comparison, it is recommended that 25 pulled hairs and 25 combed/naturally shed hairs from various areas of the head (and beard, if present) or pubic region be collected.

To collect pulled hairs, be sure to wear new, unused, clean latex or nitrile gloves and pull 25 hairs (or have the suspect or person of interest do it themselves) from various areas of the scalp or pubic region. Place these in an evidence or pharmacy fold, place the fold in an envelope and properly label.

To collect combed or naturally shed hairs, you or the suspect (or person of interest) should take a clean, unused comb and comb their hair over a piece of clean paper. Fold the paper and the comb together and place it in a properly labeled envelope.

A buccal swab from the suspect or person of interest should also be submitted.

Some laboratories may also perform comparisons on animal hairs (check with your laboratory).

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Laboratory testing of hair:

• If there is only a questioned hair present, racial and somatic (body area) origin of the hair donor may be estimated as an investigative lead.

• A microscopical comparison of questioned and known hairs compares the similarities/differences in characteristics such as color, pigment size and distribution, the size and appearance of the cuticle and medulla, cross-sectional shape, and other microscopical aspects (diseases, artificial treatment or coloring, etc). It should be noted that correlation between questioned hairs and a known donor does NOT constitute a positive means of identification, but it does indicate an association.

• If a hair has an anagen, or growing root, it will often contain cellular material that may be suitable for nuclear DNA analysis (this hair may also be suitable for mitochondrial DNA analysis if necessary). If the root is telogen, or dormant (not actively growing), it may be suitable for mitochondrial DNA analysis only.

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Source:

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