Part of Lesson Plan: Hair - What Does it Tell the Investigator

Activity Overview / Details

When discussing the collection and analysis of hair as evidence it is important to understand the terms used by the investigator and the scientist.

Consistent: This conclusion results when the samples have similar characteristics.

Dissimilar:  Non-consistent. The two samples do not have similar characteristics.

Inconclusive:  When it cannot be determined to any degree of certainty that two samples originated from the same source.

Primary Transfer: Occurs when hair transfers from the part of the body where it is growing to either the victim or the suspect. Specifically if it transfers from the victim to the suspect or from the suspect to the victim. Examples of incidents in which a primary transfer could take place would be during a fight or sexual assault.   

Secondary Transfer:  This occurs when hair that is on the clothing of the victim or transfers to the other party. For example, picture a hair that has been shed onto the shoulders of a person and then, during a fight, the hair comes off onto the clothing of the other combatant.

Cuticle: The enveloping layer. This is the layer that also contains the scale pattern which can be used to identify the species of animal that the hair came from.

Cortex: An outer layer.

Medulla: The inner part of the hair. The medulla may also give clues as to the species of animal that the hair originated from.

Keratin:  A type of protein.

Melanin: The color or pigment of the hair.

Metallic elements: Trace quantities. Note: hair also stores evidence of ingested materials such as drugs and poisons.