hairs and fibers
TRANSCRIPT
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HAIRS AND
FIBERS
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HAIR OBJECTIVES• Recognize and understand the cuticle, cortex
and the medulla areas of hair• Describe the three phases of hair growth• Identify differences between animal and
human hairs• Explain proper collection of forensic
hair/evidence fibers• Describe and understand the role of DNA
typing in hair comparisons
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FIBERS OBJECTIVES
• Identify the difference between natural and manufactured fibers.
• Describe collection procedures for fibers
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What is Hair?
• An appendage of the skin that grows out of an organ known as the hair follicle.
• Structure – Root inside follicle– Shaft– Tip End
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SHAFT STRUCTURE
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Cuticle• The scale structure covering the exterior of the hair.
• Overlapping scales that always point toward the tip end of each hair.
* Formed from specialized cells that have hardened and flattened as the hair grows
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Cuticle (or scale) Pattern will not individually identify a suspect
One of the factors used to differentiate between Human and Animal Hair
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CORTEX
• Contains pigment granules
• Granules are used for points of comparison– Color– Size– Distribution
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MEDULLA
• Central canal of cells• Not always present– If present, not always consistent
• Diameter is known as Medullary Index– Human Index is less than 1/3 – Animal Index is ½ or greater
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TYPES OF MEDULLAS
• A) Fragmented– Uneven breaks in the
medulla• B) Interrupted– Even breaks in the
medulla• C) Continuous– Always constant
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HAIR GROWTH PHASES• Anagen
– Initial growth phase– Hair actively produced– Up to 6 years– Follicular Tag for DNA
• Catagen– Transition between An and Tel– Growth retards– Hair separates from blood
supply– Lasts 1-2 weeks
• Telogen– Hair growth ends– Hair sheds– 2-6 months
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HAIR ANALYSIS
• 1) Determine whether it is human or animal hair– HOW?
• Scale Pattern• Medulla Shape• Medulla Index
• 2) Determine hair origin• 3) Compare hair sample to known reference
standards– Must come from same area of body
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Race Ancestry Medulla Pigmentation Cross Section
Caucasoid European Frag/Not Present Straight or Wavy, Fine coarse, more evenly
distributed than Negroid
Oval/Round
Mongoloid Asian Continuous Very Dense, even distribution
Thick cross section
Negroid African Frag/Not Present Kinky, dense, unevenly
distributed
Flat/Oval
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EVIDENCE COLLECTION
• 50 full length from head• 24 full length from pubic area• Reference samples MUST BE from same area
of the body
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FIBERS
• Class of materials that are continuous filaments or are in a discrete elongated pieces, similar to lengths of threads.
• Different Types– Natural Fibers– Manufactured Fibers
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FIBERS
• Manufactured– Derived from either
natural or synthetic polymers
– Consists of regenerated (raw materials) and synthetic fibers (polymers)
– Acrylic, Rayon, Acetate
• Natural– Derived from animal or
plant– Same procedure as
human hair– Most common is cotton– Linen and wool
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FIBER ANALYSIS
• PLM or Comparison microscope used• Study – Cross section– Presence of specific particles– Color– Diameter– Striations on surface of fiber
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FIBERS ANALYZED USING PLM
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Cotton
LinenWool
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FIBER COLLECTION
• Use a vacuum to collect fibers.• Also use:– Scraping – Tape lift– Picking– Shaking