Hair.

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Presentation transcript:

Hair

Kendall/Hunt Publishing Company Introduction Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the crime. From hair one can determine: If the source is human or animal Race (sometimes) Origin of the location on the source’s body Whether the hair was forcibly removed If the hair has been treated with chemicals If drugs have been ingested Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company Hair Shaft Composed of: Cuticle—outside covering, made of overlapping scales Cortex—inner layer made of keratin and imbedded with pigment; also contains air sacs called cortical fusi Medulla—inside layer running down the center of the cortex Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company The Cuticle The cuticle is the outermost layer of hair which is covered with scales. The scales point toward the tip of the hair. Scales differ between species of animals and are named based on their appearance. The three basic patterns are: Coronal Spinous Imbricate Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company The Cortex Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company The Medulla The medulla is the hair core that is not always visible. The medulla comes in different types and patterns. (like the lead in a pencil) Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company Human Medulla Human medulla may be continuous, fragmented or absent. Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company Hair Growth Terminology Anagen—hair that is actively growing; lasting up to 5 years Catagen—hair is not growing; a resting phase Telogen—hair that is dying and ready to fall out; lasting two to six months Grows about 0.5 mm per day or 1 centimeter per month; approximately one half inch per month Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company The Root Human roots look different based on whether they have been forcibly removed or if they are telogen hairs and have fallen out. Animal roots will vary, but in general have a spear shape. Fallen out Forcibly removed Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company Hair Comparison Color Length Diameter Distribution, shape and color intensity of pigment granules Dyed hair has color in cuticle and cortex Bleaching removes pigment and gives a yellow tint Scale types Presence or absence of medulla Medullary type Medullary pattern Medullary index Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company DNA from Hair The root contains nuclear DNA. If the hair has been forcibly removed, some folicular tissue may be attached containing DNA. The hair shaft contains abundant mitochondrial DNA, inherited only from the mother. It can be typed by comparing relatives if no DNA from the body is available. This process is more difficult and costly than using nuclear DNA. Kendall/Hunt Publishing Company