Hair specimens

Hair left at a crime scene can be important evidence in a forensic investigation. A strand of hair can indicate the age, sex, and race of the person from which it came. Microscopic examination of hair found at a crime scene can confirm that a suspect was at a scene. Not all hair evidence has to be human hair, for example, cat hair found at the scene of a robbery may match the cat hair found on a suspect’s coat. Try the following activity to see how hair is used as evidence in an investigation.

Materials

- strand of hair from several people or animals
- transparent tape
- several sheets of white paper
- marking pen
- magnifying lens
- microscope (optional)
- pen or pencil
- notebook

Procedure

1. Obtain strands of hair from several people. You can take some from their hairbrushes, or cut or pull with permission, several hairs from each head. Include pet hairs in your investigation, if possible.
2. Tape each strand of hair to a sheet of white paper. With the marking pen, label the hair according to whose it is and how it was obtained.
3. Examine each hair with the magnifying lens and microscope, if available. Record your observations in your notebook.

More Fun Stuff to Do

Ask a helper to choose someone who already gave you a hair sample and obtain another strand of hair from that person. Using your labeled samples and magnifying lens or microscope can you identify this person after comparing all samples?

Explanation

The first step in any laboratory examination of hair evidence is for the crime lab to determine whether it is human hair. This is done by first comparing the hair to known human samples. The next step is to note the features of hair, such as its length, diameter, and color, including the distribution of color (hair may be lighter on one end) and any evidence of dyeing or bleaching.

Hair that has been pulled from the scalp-as opposed to hair that has been cut or broken off, or that has naturally fallen out-will often have tissue sticking to the root (the enlarged part of the strand of hair that grows below the surface of the skin). This tissue can be used to identify the owner of the hair through forensic techniques such as blood factor analysis and DNA testing.