Introduction

 Hair is mainly composed of a protein called Keratin, which is the same protein that makes up your fingernails and the horn on a Rhinoceros! While hair may look very diverse, it actually has the same morphology, or structure, in all humans. The three main parts of the hair are the cuticle, the cortex, and the medulla. To visualize the structure of a hair, think of it as a pencil. The outer thin layer known as the cuticle, is similar to the paint on the pencil. The next layer, containing the pigments is the cortex, and it would be respresented as the wooden part of the pencil. Finally, the innermost layer, known as the medulla, can be thought of as the lead in the pencil. Hair evidence is tricky and can be both class and individual evidence. Part of the hair cycle that makes this evidence so tricky is that everyone routinely sheds hair which means that hair is everywhere. Even if a hair has nuclear DNA attached, it is often difficult to show that the hair actually belonged to the perpetrator of the crime and not someone who merely passed by the crime scene. Fibers and botanical remains are also often found at crime scenes, and just like hair evidence, can become cumbersome to analyze due to their abundance. Cotton is the most common fiber found, and is even a large componenet of household dust! Some cases have remarkable and unique fiber or botanical evidence, but this is not often the case. A Forensic Investigator certainly has to remember the limits of this type of trace evidence when investigating a crime scene!

Essential Questions

• What are the parts of a hair and how does it grow?
• How is hair evidence collected and analyzed?
• What are the different types of fibers typically found in a crime scene?
• How is fiber evidence collected and analyzed?
• What botanical remains are typically found in a crime scene and how are they analyzed?

Module Minute

Hair is an abundant type of trace evidence found at nearly all crime scenes. The abundance of hair in crime scenes, and the fact that everyone routinely sheds hair as part of the hair growth cycle, makes it very difficult to separate hair samples from the victim and their associates from those left by the perpetrator. Hair evidence based solely on morphology can't be used to identify an individual. In a morphological match, it can only be said that the hair sample from the crime scene is consistent with the suspect hair sample. To identify an individual from a hair sample, nuclear DNA must be obtained from the hair follicle. Fibers found at the crime scene often present challenges to investigators. Fibers can sometimes be linked to a suspect if the fiber is sufficiently unique and is found in the suspect's possession and at the crime scene.

Georgia Virtual, Analysis of Hair, Fibers, and Botanical Materials, CC BY-NC-SA 3.0