The Wonderful World of Hairs
and Fibers
Different Scopes used to analyze
hair and fiber
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Compound light
Comparison
Dissecting
Polarized
Scanning Electron Microscope (SEM)
Stages of Hair “Life”
• Anagen
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–
–
–
Growing stage
Up to 6 years possible
Root shaped like “flame”
Hair grows ~1cm/month (1” every 10 weeks)
Stages of Hair “Life”
• 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
Human Hair Parts
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•
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4
1. Root
2. Follicle
3. Shaft
4. Tip
2
1
3
Human Hair Parts
1
•
•
•
•
1. Distal (tip)
2. Proximal (root end)
3. Medulla
4. Cuticle (contains
scale pattern)
• 5. Cortex
4
3
5
2
Scale patterns
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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
Deer
Muskrat
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
Pulled Hair
Anagen Stage
Telogen stage
Razor, Cut hair & Split hair
Split
Razor
Cut
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 life
Dust 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