Hair Analysis

Hairs collected at the scene of the crime can provide investigative information about the donor when trying to develop a suspect in a case. The average person naturally sheds about 100 hairs a day, which makes it possible that the perpetrator's hair will be found at a crime scene or transferred onto the clothing of the victim. Hair can be transferred from pubic area to pubic area during sexual assaults, or it can be forcibly removed during a vicious struggle. With a microscope and strict scrutiny, a hair can reveal details about its origin. Examination can reveal whether the hair is animal or human. If the hair is of human origin, the race of the donor and the area of the body from which it originated can be determined. Microscopical examination can also determine if the hair was cut, pulled, naturally shed, if it originated from a living or dead person, if the hair has been subjected to artificial treatments such as bleaching, coloring or permanent waves. Damage due to disease or exposure to fire can also be detected. All this information can be important to the investigators when they know nothing about the perpetrator of a crime.

If a suspect has already been identified and it is desired that questioned hairs be compared to the suspect, known hair from that suspect will be required to perform a microscopical comparison.  Comparison of the questioned hair to the known hair may allow a conclusion that the questioned hair possibly originated from a particular person (support contact between victim and suspect).  It may also exclude hair as meaningful to the investigation, i.e. hair found on victim is like the victim’s own hair.  Any significant matching hairs will then be sent to the Biology section for nuclear DNA analysis if the root has follicular material present.  If no follicular material is present, the matching hair will be sent to a FBI partner laboratory for mitochondrial DNA analysis.