Hairs & Fibers

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					Hairs & Fibers
Morphology and Structure of Hair
Morphology of Hair

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

                             Extends    from its
                             root or bulb
                             embedded in the
                             follicle, continues into
                             a shaft, and
                             terminates at a tip
The Shaft of Hair

            Composed of three
             layers: cuticle,
             cortex, and
                    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
                  Preserving scale pattern

   Since examination of
    internal structure of hair
    requires loss of scale
    pattern, a scale case is
   Clear nail polish on
    microscope slide
   Hair embedded and
    allowed to dry before
          Differences between animal hairs and human hairs
   There are three basic scale structures that
    make up the cuticle—coronal (crown-like),
    spinous (petal-like), and imbricate
    (flattened). Combinations and variations of
    these types are possible.

                    Differences between animal hairs and human hairs
   The coronal, or crown-like scale pattern is
    found in hairs of very fine diameter and
    resemble a stack of paper cups. Coronal
    scales are commonly found in the hairs of
    small rodents and bats but rarely in
    human hairs.
                        Differences between animal hairs and human hairs
    Spinous or petal-like scales are triangular
     in shape and protrude from the hair shaft.
     They are found at the proximal region of
     mink hairs and on the fur hairs of seals,
     cats, and some other animals. They are
     never found in human hairs.
          Differences between animal hairs and human hairs
   The imbricate or flattened scales type
    consists of overlapping scales with narrow
    margins. They are commonly found in
    human hairs and many animal hairs.
       Differences between animal hairs and human hairs
   Human hairs are generally consistent in color
    and pigmentation throughout the length of the
    hair shaft, whereas animal hairs may exhibit
    radical color changes in a short distance, called
   The distribution and density of pigment in
    animal hairs can also be identifiable features.
    The pigmentation of human hairs is evenly
    distributed, or slightly more dense toward the
    cuticle, whereas the pigmentation of animal
    hairs is more centrally distributed, although
    more dense toward the medulla.
   The medulla, when present in human hairs, is
    amorphous in appearance, and the width is
    generally less than one-third the overall
    diameter of the hair shaft. The medulla in
    animal hairs is normally continuous and
    structured and generally occupies an area of
    greater than one-third the overall diameter of
    the hair shaft.
                Morphology: Cortex
   Made of spindle-shaped
    cells aligned in a
    regular array, parallel
    to the length of the hair
   Embedded with
    pigment granules that
    give hair its color
   The color, shape and
    distribution of the
    granules provide points
    for forensic comparison
   Your natural Hair color is
  determined by three factors

1. The type of natural color pigment
  melanin present in your hair's cortex.
    Eumelanin (black pigment)

    Phenomelanin (red/yellow
2. How many melanin granules exist
3. Whether those granules are close
  together or far apart
How Melanin pigments determine your
         natural haircolor:

    Black hair contains densely packed melanin granules full of

    Brown hair has a loose pattern of eumelanin-filled
     granules or granules blended with eumelanin and
     phenomelanin, depending upon its cool or warm tones and
     its darkness or lightness.

    Blonde hair contains few granules with minimal bits of
     eumelanin. In fact, the eumelanin is so sparse that the
     color of blonde hair is the color of the hair fiber itself.

    Red hair has loosely packed granules containing
     What causes gray hair?
   As you age, your natural production of
    pigment slows down and your natural
    color loses its color strength.

   This doesn't happen to every hair at the
    same time, so the contrast between the
    hair with no color and the hair that still
    has some color causes it to look gray.

   So how gray your hair actually looks is
    determined by the percentage of strands
    with no color vs. the pigmented strands.
               Morphology: Medulla

   canal like structure of cells that runs
    through the center of the cortex
                   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 < 1/3
       Animals: medullary index > 1/2
Medullae of Different
            Medulla Shape
   Medulla shape is another characteristic
    that varies from species to species
                             UNISERIAL (rabbit)

                             MULTISERIAL (rabbit)

                             VACUOLATED (dog, fox,

                             LATTICE (deer)

                             AMORPHOUS (human,
                             common)                 20
Medulla of Different Species
            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 whose medulla is usually continuous
   Most animals have medulla that is continuous or
   The shape of the medulla can help identify a
   Examples:
        Most animals and humans: cylindrical
        Cats: pearl shape
        Deer: spherical occupying whole hair shaft
Comparison of Animal and Human

Medullary Index ≥1/2                             Medullary Index <1/3
Medulla is present for all                       Medulla is absent for
animals                      Medulla is
                             fragmented – only   most humans
                             some animals and
Medulla is continuous for    humans
most animals                 Medulla is
                                                 Medulla is continuous
                             cylindrical in      for Mongoloid race
Medulla is patterned for     shape (most
most animals
       Identification and Comparison of Hair
   Morphological Characteristics do not allow
    individualization of a human hair to any single head
    or body
   Hair when collected with an adequate number of
    standards/references can provide strong
    circumstantial evidence
   Scale structure, medullary index, and medullary
    shape are most often used for hair comparison
   Evidential value lies with degree of probability
    associated with a questioned hair and an particular
   11 percent of all morphological hair matches are
    generally found to be non-matches—meaning
    microscopic hair comparisons are presumptive in
    nature—must be confirmed by DNA comparisons
             Human Hairs

   Racial Determination
   Body Area
   Age and Sex?
   Forcibly Removed?
          Can the racial origin of hair be determined?
   Forensic terms:
    Caucasoid, Negroid,
   Mongoloid has
    continuous medullae
   Caucasian has even
    distribution of pigment in
   Negroid has unevenly
    distributed pigment.
            Racial Determination
              Usually kinky,
              containing dense,
              unevenly distributed                 Mongoloid

              Cross section is flat
              to oval in shape.                   Usually coarse
Usually straight or wavy
                                                  larger in size
with very fine to coarse
pigments that are more
evenly distributed .
                                                  Cross sections
Cross section are oval to                         are round in
round in shape.                       Caucasoid
                        Head Hairs
   Long with moderate shaft diameter and diameter variation

   Medulla absent to continuous and relatively narrow when compared
    to the structure of hairs from other body areas

   Often with cut or split tips

   Can show artificial treatment, solar bleaching, or mechanical

   Soft texture, pliable
  Pubic Hairs
                          Shaft diameter
                          coarse with
Medulla relatively        wide
broad and usually         variations and
continuous when           buckling

                                           Root frequently
                                           with tag

Tip usually tapered, rounded, or

Stiff texture, wiry
                    Limb Hairs
Diameter fine with little     Medulla is
variation                     discontinuous to trace
                              with a granular
Gross appearance of hair is   appearance
arc-like in shape

Soft texture
Tips usually
tapered, often
blunt and
abraded, rounded
scale ends due to
     Facial Hairs (Beard/Mustache)
   Diameter very coarse with irregular
    or triangular cross-sectional shape

   Medulla very broad and continuous,
    may be doubled
                           Chest Hairs
   Shaft diameter moderate and variable

   Tip often darker in color, long and fine,

   Medulla may be granular

   Stiff texture
Axillary or Underarm Hairs
   Resemble pubic hairs in general appearance, but
    less wiry

   Medullary appearance similar to limb hairs

   Diameter moderate and variable with less
    buckling than pubic hairs

   Tips long and fine, frequently with bleached
                         Other Body Hairs

   Eyebrow: Stubby, some diameter
    fluctuation, saber-like in appearance

   Eyelash: Short, stubby with little
    shaft diameter fluctuation, saber-like
    in appearance

Trunk: A combination of features of limb and
pubic hairs, a transitional hair
             Tip of the Shaft


    Burned        Cut    Razored   Split
                       Root of Hair
   Provide the tools to produce hair and continue its
   3 Stages of Growth (different looking roots)
       Anagen -initial phase may last up to 6 years, root is
        flame shaped
       Catagen –transition phase (2-3 weeks), root is
       Telogen –phase where hair naturally falls out of the
        skin, root is club-shaped
Hair Growth Cycle
       Forcibly Removed?


    Pulled   Forcibly Removed   Shed
                                 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

                                            An anagen hair that has been
                                            plucked out: notice the soft,
                                            sticky tail
Collection of Hair Evidence
      Collection of Hair Evidence

   Questioned and Reference hair must come
    from same area of the body; one cannot,
    for instance compare head hair to pubic
   The collection of 50 full length hairs from
    all areas of the scalp will normally ensure
    a representative sampling of head hair.
       Collection of Hair Evidence

   A minimum collection of 24 full length
    pubic hairs should cover the range of
    characteristics present in this type of hair.
   All collected hairs must be full-length so
    that the investigator can see if the color
    and morphological features vary
    throughout the length of the hair.
    Packaging of Hair Evidence
   Recover all hair present.
   If possible, use fingers or tweezers to pick up
    hair, place in paper bindles or coin envelopes
    which should then be folded and sealed in
    larger envelopes.
   Label the outer sealed envelope.
   If hair is attached, such as in dry blood, or
    caught in metal or a crack of glass, do not
    attempt to remove it but rather leave hair intact
    on the object.
    If the object is small, mark it, wrap it, and seal
    it in an envelope.
   If the object is large, wrap the area containing
    the hair in paper to prevent loss of hairs during
                                                    Fibers: Natural
        Derived entirely from animal or
         plant sources
        Most prevalent plant fiber is
        Its widespread use has made its
         evidential value almost                                                                                         Cotton

        Cotton has a ribbon-like shape with
         twists at regular intervals
        Animal sources include sheep                                                                                     Wool
         (wool), goats (mohair, cashmere)
         and many other sources
                                            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)
                  Man-Made Fibers Con’t
   Regenerated Fibers
       Made from regenerated cellulose (wood or cotton
       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
        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 fiber—ex. 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
   ID and Comparison of Man-Made Fibers con’t.

The chemical makeup of the fiber itself can be
  examined through the following:
 Infrared microspectrophotometry

 Refractive Index

The chemical makeup of the dyes in the fiber can
  be examined through the following:
 Liquid chromatography

 Visible light microspectrophotometry

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