Hair and Fiber evidence

What are the three components of the hair?

Root, Follicle, Shaft

What are the three layers of the hair shaft?

Cuticle, Cortex, Medulla

What is the function of the cuticle?

Protects the hair and helps retain its features

Why is the cuticle important in forensic science?

It makes hair resistant to decomposition and chemicals

What are the three patterns of cuticle?

Coronal, Spinous, Imbricate

What is the cortex made up of?

Spindle-shaped cells embedded with pigment granules

What does the cortex give hair?

Color

What are the key points of comparison in forensic analysis in the cortex?

Size, shape, and distribution of pigment granules

What does bleaching do to the hair?

Removes pigment granules and gives it a lighter, yellow tint

Where does the medulla run through?

The center of the hair shaft

What are the classifications of human medulla patterns?

Continuous, Interrupted, Fragmented, Absent

Can the medulla be used for individual identification?

No, but it can be used for species identification

What is the formula to calculate medullary index?

MI = width of medulla/width of entire hair

If medullary index is 0.5 or greater, then the hair is...

Animal

If the medullary index is 0.33 or less, then the hair is...

Human

Where is the root located?

Within the follicle

What is the function of the root?

Anchors the hair and helps with growth

What is the function of the follicular tag?

Can be used for individual identification

Anagen phase

Initial growth phase of hair when hair is actively growing

Catagen phase

Transition stage of hair growth

Telogen phase

Final phase of hair growth when hair naturally sheds

Appearance of pubic hairs

curly, coarse; high variation in diameter; typically have fragmented medullae

Appearance of head hairs

straight to wavy; low variation in diameter; typically have continuous medullae

Appearance of facial hairs

have oval cross-sections and pointed tips (from shaving or trimming)

True or False: Race can always be determined from hair

False

Caucasian Hair Characteristics

Straight/wavy; round or oval cross-sections with very evenly distributed pigments

African Hair Characteristics

Curly or coily; oval or elliptical cross-sections with unevenly distributed pigments

Asian Hair Characteristics

Straight; round cross-sections with dense pigments

The only age group that can be determined through hair analysis

Infant

True or False: Sex can be determined from hair analysis.

False

Fibers derived from animal and/or plant sources

Natural fibers

Fibers derived from modified natural fibers or synthetic fibers

Manufactured/synthetic fibers

Test that separates different colors in dye

Chromatography

Test that measures unique refractive index (speed of light through a material)

Birefringence

Test that measures pattern of light absorption

Infrared absorption

Test used to detect trace amounts of drugs/toxins/poisons in hair samples by bombarding the sample with radiation

neutron activation analysis