Chapter 3: The Study of Hair

• Trace Evidence • Class Evidence

• can be easily left behind • secondary transfer (common w/ animal hair) • does not easily compose • offers clues to racial background • chemical tests (drugs, heavy metals, nutritional deficiencies) • DNA (if follicle is present)

• regulates body temperature • decreases friction • protects against sunlight • acts as a sense organ

• Hair shaft • Sebaceous Gland • Follicle • Papilla

structure in the skin

made of (Keratin) > a protein produced in the skin

contain the blood vessels that supply the nutrients to feed the hair & help it grow

secretes oil & helps to keep the hair conditioned

made up of amino acids in a spiral shape

• Cuticles • Cortex • Medulla • Pigment granules made of melanin

• Cuticle • Cortex • Medulla

• the transparent outer layer of the hair shaft • made up of scales that overlap each other and protect the inner layers of the hair • human hair has a cuticle scales that are flattened & narrow which are called imbricated (animal hair is diff.)

• the largest part of the hair shaft • part of the hair that contains the pigment or melanin that gives the hair its color • amount of pigment varies from person to person

• center of the hair • can be hollow or filled w/ cells • 5 diff. medulla patterns

• Continuous • Interrupted (Intermittent) • Fragmented or Segmented • Solid • None

one unbroken line of color

pigmented line broken at regular intervals

pigmented line unevenly spaced

no separate pigmentation in the medulla

• Shape • Length • Diameter • Texture • Color

circular or elliptical cross section

circular w/ tapered ends

thick & triangular/coarse/double medulla - underarm - body hair

• bleaching hair removes pigment & gives hair a yellow color (hair is brittle/disturbs the scales on cuticle) • changes the color of the hair shaft • cuticle & cortex take on the color of the dye