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
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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