The Wonderful World of Hairs and Fibers

Different Scopes used to analyze hair and fiber

• Compound light

• Comparison

• Dissecting

• Polarized

• Scanning Electron Microscope (SEM)

Stages of Hair “Life”

• Anagen– Growing stage– Up to 6 years possible– Root shaped like “flame”– Hair grows ~1cm/month (1” every 10 weeks)

• Catagen– ~3 weeks long– Dormant, resting stage– Root gets longer and thinner

Stages of Hair “Life”

• Telogen– ~6 months– Root

• Club shaped

• Pushes out and is shed

– Lose approximately 70 hairs/day

Stages of Hair “Life”

Human Hair Parts

• 1. Root• 2. Follicle• 3. Shaft• 4. Tip

1

2 3

4

Human Hair Parts

• 1. Distal (tip)• 2. Proximal (root end)• 3. Medulla• 4. Cuticle (contains

scale pattern)• 5. Cortex

1

2

3

4

5

Scale patterns

• Imbricated

• Mosaic

• Petal

• Pectinate

• Chevron

Medulla Types

• Continuous

• Fragmented

• Intermittent/interrupted

Medullary Index of Hair

• To find the MI– Diameter of medulla/hair shaft diameter

• Humans = <1/3

• Other animals = >1/2

• Classify Medulla as:– Continuous, Interrupted, Fragmented, or Absent

Example Medulla Patterns that can be seen

• Lattice

• Vacuolated

• Uniserial

• Multiserial

Deer, Dog & Muskrat hair

Muskrat

Deer

Which is Caucasian, Negroid, Mongoloid Head Hair?

Caucasian, Europeans, Mexicans,

Middle Easterners: oval to round

Negroid, Africans oval to flat

Mongoloid, Orientals,

American Indians: round

Pulled Hair v. Shed Hair

Telogen stage

Anagen StagePulled Hair

Razor, Cut hair & Split hair

Razor

Cut

Split

Human eyebrow

Burned hair

Buckling of hair seen in pubic hair

Hair match

• This is the view that a comparison scope can give when comparing two matching hairs

The small things in lifeDust Mite

Eyelash mites

Bedbug feeding on flesh

Fibers

Types of fibers

• Natural fibers– Animal fibers are most common at crime scene

• Man-made

Natural fibers

• Animal:– Wool from sheep most common– Goats, camel, alpaca, rabbit, mink, llamas, beaver

• Plant:– Cotton most common– Flax (linen), ramie, sisal, jute, hemp

• Excrement:– Silk from silkworm (cellulose from mulberry leaves)

• Mineral:– Asbestos

Cotton fibers cross-section

Wool fibers v. Cotton fibers

Wool Cotton

Flax Fibers

Hemp fibers

Silk fibers

• Raw thrown

• Wild silk

Asbestos fibers

Man-Made fibers

• Regenerated fibers– Machine made from natural materials like cotton or

wood

– 1910 rayon, then acetate, then triacetate

• Synthetic fibers– Most fibers are made synthetically from chemicals

– 1939 nylon, then polyester and acrylic

– Shape or cross-section can determine value of the fiber; manufacturer specific

Nylon fiber cross sections

Acetate Fibers

Nylon fibers

Orlon Fibers

Polypropylene fibers