Analysis of Hair, Fiber and Botanical Materials Module Overview

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 represented 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 component 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?

Key Terms

Cuticle - The scale structure covering the exterior of the hair.
Cortex - The main body of the hair shaft, contains pigment and cortical fusi, gives hair its shape.
Medulla - A cellular column running through the center of the hair. It is not always present in humans, and can be used to tell different species of animals apart.
Anagen Phase - The initial growth phase during which the hair follicle actively produces hair and hair grows.
Catagen Phase - A transition phase between the anagen and telogen phases of hair growth hair is at rest and not actively growing.
Telogen Phase - The final growth phase in which hair naturally falls out of the skin.
Follicular Tag - A translucent piece of tissues surrounding the hair's shaft near the root that contains the richest source of DNA associated with hair.
Nuclear DNA - DNA that is present in the nucleus of a cell and that is inherited from both parents.
Natural Fibers - Fibers derived entirely from animal or plant sources
Manufactured Fibers - Fibers derived from either natural or synthetic polymers.
Polymer - Substance composed of a large number of atoms that are usually arranged in repeating units.
Monomer - Basic unit of structure from which a polymer is constructed.
Follicle - Structure from which hair grows, only part of hair that contains nuclear DNA.
Melanin - Pigment granules in the cortex that give hair its color.
Cortical Fusi - Air spaces usually found near the root but may be found throughout the hair shaft.
Medullary Index - Determined by measuring diameter of the medulla and dividing by the diameter of the hair. Humans have less than .3 or 1/3 and animals have more than 1/2 or .5
Morphology - Structural characteristics in the case of the morphology of hair; it can't be used to identify individuals.
Keratin -A type of fibrous protein that makes up the majority of the cortex of a hair.
Trichology - The branch of medical and cosmetic study and practice concerned with the hair and scalp.
Lanugo - A coat of delicate, downy hairs, esp. that with which the human fetus is covered.
Vellus - The fine hair present on the body before puberty.
Terminal Hair - One of three types of hair in humans based on hair size, time of appearance, and structural variations. Terminal hair is the larger, coarser hair in the adult that replaces the vellus hair.
Sebaceous Gland - A small gland in the skin which secretes a lubricating oily matter (sebum) into the hair follicles to lubricate the skin and hair.
Coronal Scales - Crown-like scale pattern is found in hairs of very fine diameter and resemble a stack of paper cups. Coronal scales are commonly found in the hairs of small rodents and bats but rarely in human hairs.
Spinous Scales - Petal-like scales are triangular in shape and protrude from the hair shaft. They are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs.
Imbricate Scales - Scales that have overlapping edges, as tiles on a roof or scales on a fish.
Textile - Artifact made by weaving or felting or knitting or crocheting natural or synthetic fibers.
Papilla - The papilla is a large structure at the base of the hair follicle where hair grows from. The papilla is made up mainly of connective tissue and a capillary loop.
Erector Pili - Tiny muscle fibers attached to each hair follicle, which contract to make the hairs stand on end, causing goose bumps. They exist in most mammals including humans.

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