2.3 - HAIRS AND FIBERS

Keratin

Hair is composed of the protein _____, which is also the primary component of finger and nails. 

hair follicle

Hair is produced from a structure called the ______

• root

• mitochondrial DNA

• In order to test hair evidence for nuclear DNA, the ___must be present. 

• The hair may also be tested using _________ whether or not the root is present. 

Keratin

Is a family of fibrous structural proteins. 

• Cuticle

• Cortex

• Medulla

HAIR STRUCTURES:

Cuticle

outer coating composed of overlapping scales

Cortex

protein-rich structure around the medulla that contains pigment

Medulla

central core (may be absent) 

Animal HAIR

Pigmentation is denser toward the medulla

Animal hair abruptly can change colors in banded patterns.

Thicker Medullary Index  > 0.5

Human HAIR

it tends to be denser toward the cuticle

can change colors in banded patterns

Thinner Medullary Index  <0.33

Anagen

hair that is actively growing

• lasting 3 to 5 years (80-90% of a person’s hair will be in this phase) 

Catagen

hair is not growing;

a resting phase 

Telogen

hair that is dying and ready to fall out

• lasting two to six months

hair shaft

Hair consists of a _________ produced by a follicle embedded in the skin.  

• The shaft consists of an outer cuticle, a cortex, and an inner medulla.  

Fiber

is the smallest unit of a textile material

• that has a length many times greater than its diameter.

• can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric.  

Natural fibers

come from plants and animals

are used in the production of fabric.

Cotton fibers

are the plant fibers

most used in textile materials 

 

Wool

The most frequently used animal fiber in the production of textile materials is ____,

• and the most common fibers originate from sheep. 

Synthetic

More than half of all fibers used in the production of textile materials are synthetic or man-made.  

• Nylon, rayon, and polyester are all examples of synthetic fibers. 

Fiber Evidence

are gathered at a crime scene with tweezers, tape, or a vacuum.  

• They generally come from clothing, drapery, wigs, carpeting, furniture, and blankets.   

• For analysis, they are first determined to be natural, manufactured, or a mix of both.

Fiber Numbers

The greater the number of fibers, the more likely that contact actually occurred

between these individuals