Hairs

1
Hairs Fibers
2
Purpose of Hair

• Hair on mammals -
• helps to regulate body temperature
• decrease friction
• protect against sunlight
• Location of hair on humans
• Head
• Eyebrows and eyelashes
• Mustache and beard
• Underarms
• Auxillary (overall body)
• Pubic

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Morphology of Hair

• An appendage of the skin that grows out of an
  organ known as the hair follicle.

• Hair - extends from root or bulb embedded in the
  follicle, continues into a shaft, and terminates
  at a tip end.

4
The Shaft of Hair

• Composed of three layers cuticle, cortex, and
  medulla.

5
Structure of Hair

• Cuticle thin outer layer
• Cortex thicker middle layer
• Medulla inner layer

6
Morphology Cuticle

• Protective coating made of overlapping scales,
  produce a characteristic pattern
• Scales always point toward tip of hair
• Not useful in individualizing human hair
• Can be used for species identification

http//www.pg.com/science/haircare/hair_twh_35/hai
r_twh_35_02.jpg
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Preserving scale pattern

• Since examination of internal structure of hair
  requires loss of scale pattern, a scale case is
  made.
• Clear nail polish on microscope slide
• Hair embedded and allowed to dry before removed.

8
Cuticle - Scales

• Three basic scale structures that make up the
  cuticle
• coronal (crown-like)
• spinous (petal-like)
• imbricate (flattened)
• Combinations and variations of these types are
  possible.

http//www.fbi.gov/hq/lab/fsc/backissu/jan2004/res
earch/2004_01_research01b.htm
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Cuticle - Scales

• The coronal, or crown-like scale pattern
• found in hairs of very fine diameter and resemble
  a stack of paper cups.
• commonly found in
• hairs of small rodents and bats but-
• rarely in human hairs

http//www.fbi.gov/hq/lab/fsc/backissu/jan2004/res
earch/2004_01_research01b.htm
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Cuticle - Scales

• Spinous or petal-like scales
• triangular in shape and protrude from the hair
  shaft.
• Found at the proximal region of mink hairs and on
  the fur hairs of seals, cats, and some other
  animals.
• Never found in human hairs!!

http//www.fbi.gov/hq/lab/fsc/backissu/jan2004/res
earch/2004_01_research01b.htm
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Cuticle - Scales

• Imbricate or flattened scales
• Consists of overlapping scales with narrow
  margins
• commonly found in human hairs and many animal
  hairs.

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Morphology Cortex

• Embedded with pigment granules that give hair its
  color
• Three things for forensic comparison
• color
• shape
• distribution of the granules

www.pg.com/science/haircare/hair_twh_59.htm
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Morphology Medulla

• canal like structure of cells that runs through
  the center of the cortex

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Types of Medulla

• The medulla (the inner section) can be hollow or
  filled, absent, fragmented, continuous, doubled,
  pigmented, or un- pigmented.

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Medullary Index

• Measure of the diameter of the medulla relative
  to the diameter of the hair shaft
• Usually expressed as a fraction
• Humans medullary index lt 1/3
• Animals medullary index gt 1/2

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Medullae of Different Species
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Medulla Shape

• Medulla shape is another characteristic that
  varies from species to species

UNISERIAL (rabbit)
MULTISERIAL (rabbit)
VACUOLATED (dog, fox, common)
LATTICE (deer)
AMORPHOUS (human, common)
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18
Medulla of Different Species
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Forensic Analysis of Medulla

• Presence of medulla varies quite a bit even hair
  to hair
• Human head hairs generally have no medulla or may
  be fragmented ones
• except Mongoloid (Asian) race - medulla is
  usually continuous
• Most animals - medulla that is continuous or
  interrupted
• The shape of the medulla can help identify a
  species
• Examples
• Most animals and humans cylindrical
• Cats pearl shape
• Deer spherical occupying whole hair shaft

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Root of Hair

• Provide the tools to produce hair and continue
  its growth
• 3 Stages of Growth (different looking roots)
• Anagen -initial phase may last up to 6 years,
  root is flame shaped
• The cells around the follicle rapidly divide and
  deposit materials in the hair.
• Catagen transition phase (2-3 weeks), root is
  elongated
• Telogen phase where hair naturally falls out of
  the skin, root is club-shaped
• During this stage, hairs easily can be lost.

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Hair Growth Cycle
22
Root Anagen Phase

• When pulled this root may contain a follicular
  tag (rich source of DNA)
• Root is flame shaped

Anagen hair root
Root w/ follicular tag
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Human Hairs

• Racial Determination
• Age and Sex?
• Forcibly Removed?
• Can Hairs be Individualized?

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Can the racial origin of hair be determined?

• Forensic terms Caucasoid, Negroid, Mongoloid
• Mongoloid
• continuous medullae
• Caucasian
• even distribution of pigment in cortex
• Negroid
• unevenly distributed pigment.

http//www.fbi.gov/hq/lab/fsc/backissu/july2000/de
edric1.htm
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Tip of the Shaft

Burned Cut
Razored Split
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Forcibly Removed?

Pulled Forcibly Removed
Shed
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Brushed-out hairs all have this kind of root.
A normal telogen hair with a hard 'club' end,
seen under (left) a light microscope and (right)
an electron microscope
This is an anagen hair, one which was pulled out
and not ready to be shed.
An anagen hair that has been plucked out notice
the soft, sticky tail
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Hair Individualization

• Nuclear DNA found in nucleus of each cell
• Follicular tag tissue adhering to root or
  follicle
• Will produce odds as one in billions or one in
  trillions
• Mitochondrial DNA found outside nucleus, passed
  from only mother to child
• Many more copies compared to nuclear DNA
• Will not individualize, but will exclude a
  significant portion of population
• Cannot microscopically distinguish similar hairs
  from people maternally related

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Can DNA individualize hair?

• Yes! In some cases
• Best evidence to have is matching morphology AND
  DNA
• We will talk much more in Chapter 13 about this!

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Collection of Hair Evidence
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Collection of Hair Evidence

• Questioned and Reference hair must come from same
  area of the body
• Cannot compare head hair to pubic hair.
• Head hairs - 50 full length hairs from all areas
  of the scalp
• Other body parts 25 full length hairs
• All collected reference hairs must be full-length
  

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Identification and Comparison of Hair

• Morphological Characteristics - do not
  individualize human hair to any single head or
  body
• Hair when collected properly - provides strong
  circumstantial evidence
• Most often used for comparison
• Scale structure
• Medullary index
• Medullary shape
• 11 percent of all morphological hair matches are
  generally found to be non-matches
• meaning microscopic hair comparisons are
  presumptive in naturemust be confirmed by DNA
  comparisons

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Using Hair in an Investigation

• Macroscopic investigation can indicate length,
  color, and curliness.
• Microscopic investigation can indicate fine
  detail in hair structure.
• Phase contrast microscopy focuses light that
  passes through objects of different refractive
  indexes
• shows the presence of dye or other treatments.
• Fluorescence microscope beam of light of a
  certain color is used to show particular
  chemicals
• Shows fine detail in hair structure
• Electron microscopes directs beams of electrons
  at sample
• provides more detail of the surface or interior
  of the sample.

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Testing for Substances in the Hair Shaft

• Neutron Activation Analysis (NAA) can determine
  concentrations of substances in the sample.
• Identifies up to 14 elements in a 2 cm strand of
  human hair
• Hair placed in nuclear reactor and bombarded with
  high energy neutrons
• Probability of two individuals having same
  concentration of 9 different elements 1 in a
  million
• Some elements Antimony, argon, bromine, copper,
  gold, manganese, silver, sodium, zinc

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• Each element gives off its own gamma radiation
  with different signals

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Testing for Substances in the Hair Shaft

• Chemical Analysis -
• Chemicals that the skin absorbs often can be
  detected by analysis of the hair shaft.
• Arsenic, lead, drugs
• Can be used to determine poisoning or drug
  exposure
• Hair shaft can establish a timeline for exposure
  to toxins.
• Human hair grows 1.3 cm per month
• If root is present, sections can be dated based
  on distance from root

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Testing the Hair Follicle

• Microscopic assessment of the follicle is
  performed first because it is cost effective and
  quick.
• If a microscopic match is found, the follicle can
  be
• blood tested and perhaps show the blood type.
• DNA analyzed to provide identification with a
  high degree of confidence.

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Fibers Natural

• Derived entirely from animal or plant sources
• Most prevalent plant fiber
• cotton.
• widespread use has made its evidential value
  almost meaningless
• Cotton has a ribbon-like shape with twists at
  regular intervals
• Animal sources
• sheep (wool), goats (mohair, cashmere) and many
  other sources

Cotton
Wool
http//www.swicofil.com/images/cotton_microscopic.
jpg
http//www.e4s.org.uk/textilesonline/content/6libr
ary/report1/images/microscope_2.gif
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Man-Made Fibers

• Fibers derived from either natural or synthetic
  polymers
• The fibers are made by forcing polymeric material
  through the holes of a spinneret
• Rayon and then nylon were the first two man-made
  fibers (year 1911)

http//www.naturalvisions.co.uk/pictures/thumbnail
/XMIC_0021_0001XX.jpg
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Man-Made Fibers Cont

• Regenerated Fibers
• Made from regenerated cellulose (wood or cotton
  pulp)
• Include such fibers as rayon, acetate, and
  triacetate
• Synthetic Fibers
• Currently manufactured
• Made from synthetic chemicals called polymers
• Include such fibers as nylons, polyesters, and
  acrylics

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Polymers

• Basic chemical substance of all synthetic fibers
• Consist of long chains of repeating molecules.
  The repeating molecular units in the polymer are
  called monomers. (see pic p210)
• Often referred as macromolecules or big
  molecules
• Countless varieties exist

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ID and Comparison of Man-Made Fibers

• Fabrics that can be fitted together at their torn
  edge are easy to match
• Microscopic comparison of color and diameter
• Comparison of lengthwise striations and pitting
  on the surface of a fiber
• The shape of the fiberex. Wayne Williams case
• Cross sections are generally helpful
• Note Combined factors of color, size, shape,
  microscopic appearance, chemical composition, and
  dye content make it very unlikely to find two
  different people wearing identical fabrics

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Tools and Techniques to Aid in Comparing Fibers

• Light infrared spectrophotometercompares colors
  and chemical composition through spectral
  patterns
• Chromatographycompares dye composition
• RefractionIDs fiber by refractive index
• Comparison microscopereveals shape, coloring,
  pitting and striations