Chapter 8 Hair, Fibers, And Paint * * Fiber Evidence

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Chapter 8Hair, Fibers, And Paint
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Introduction

• Physical evidence in a variety of crimes
• Not yet possible to individualize human hair to
  any single head or body through morphology
• Still has value as physical evidence

HAIR FIBERS AND PAINT
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Introduction

• Properly collected and submitted to the
  laboratory
• Accompanied by adequate number of standard or
  reference samples
• Provides strong corroborative evidence for
  placing individual at crime scene

HAIR FIBERS AND PAINT
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Hair Evidence
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Morphology of Hair

• Appendage of the skin
• Grows out of hair follicle
• Length of a hair
• From its root or bulb embedded in the follicle
• Continues into shaft
• Terminates at a tip end
• Shaft three layers
• Cuticle
• Cortex
• Medulla
• Most intense examination by forensic scientist

HAIR FIBERS AND PAINT
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Figure 81  Cross section of skin showing hair
growing out of a tubelike structure called the
follicle.
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Cuticle

• Resistant to chemicals
• Retains structure for long periods
• Scale structure covering exterior of hair
• Keratinized
• Flattened
• Scales always point towards the tip of the hair
• Scale pattern useful in species identification

HAIR FIBERS AND PAINT
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Cuticle Patterns Coronal

• Crown-like scale pattern
• Hairs of very fine diameter
• Resemble a stack of paper cups
• Hairs of small rodents and bats
• Rarely in human hairs

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Cuticle Patterns Spinous

• Petal-like scales
• Triangular in shape
• Protrude from the hair shaft
• Proximal region of mink hairs
• Fur hairs of seals, cats, and some other animals
• Never in human hairs

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Cuticle Patterns Imbricate

• Flattened-scale type
• Overlapping scales with narrow margins
• Commonly found in human hairs and many animal
  hairs

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Scanning EMs of Hair
Malaysian Hair
European Hair
African Hair
Chinese Hair
Indian Hair
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Scanning EMs of Hair
Rat Hair
Mouse Hair
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Scanning EMs of Hair
Hair Follicle
Cut with Electric Razor
Cut with Blade
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Cortex

• Main body of the hair shaft
• Embedded with the pigment granules that impart
  hair with color
• Color, shape, distribution of granules
• Points of comparison among the hairs of different
  individuals

HAIR FIBERS AND PAINT
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Cortex of Hair

• Found within the cuticle
• Made of spindle-shaped cortical cells aligned
  parallel to length of hair
• Within the cortex are pigment granules
• made by melanocytes that give hair its color

Cortex of a damaged hair. A split end, caused
when a hair shaft is pulled apart. Many split
ends give hair a frizzy appearance, and cause
tangles.
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Melanin Pigments Role In Haircolor

• Black hair
• densely packed melanin granules
• full of eumelanin
• Brown hair
• loose pattern of eumelanin-filled granules
• or granules blended with eumelanin and
  phenomelanin
• depending upon
• its cool or warm tones
• darkness or lightness

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Melanin Pigments Role In Haircolor

• Blonde hair
• few granules with minimal bits of eumelanin
• color of blonde hair color of the hair fiber
  itself
• Red hair
• loosely packed granules containing phenomelanin

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Hair Color Determined

• Type of melanin present in hair cortex
• Eumelanin (black pigment)
• Phenomelanin (red/yellow pigment)
• Number of melanin granules
• Spacing of granules
• close together
• far apart

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Gray Hair

• Pigment production slows
• Natural color loses color strength
• Timing varies
• Contrast between the hair with no color and the
  hair that still has some color causes it to look
  gray
• Appearance percentage of strands with no color
  vs. pigmented strands

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Medulla

• Cellular column running through the center of the
  hair
• Medullary index diameter of the medulla relative
  to diameter of the hair shaft
• Humans less than one-third the diameter of the
  shaft
• Animals one-half or greater
• May be continuous, interrupted, fragmented, or
  absent

HAIR FIBERS AND PAINT
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Medulla

• Varies from individual to individual and among
  hairs of a given individual
• Different shapes, depending the species
• Humans no medulla or fragmented
• Mongoloid continuous
• Animals continuous or interrupted

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Medulla of Hair

• Cells look like a canal running through a hair
• Not all hairs have medullae
• Classification
• continuous ( most animals, human rare, Mongoloid
  race)
• fragmented (most animals, human)
• absent (human)

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Medulla Shape

• Humans and most animals ?cylindrical
• Other animals ? patterned
• Cat medulla string of pearls
• Deer medulla round cells occupying the entire
  hair shaft

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Medullary Index

• diameter of medulla
• diameter of the hair shaft
• Medullary Index Values
• Humans lt1/3
• Most other animals 1/2

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Root

• Root and other surrounding cells in the hair
  follicle
• Tools necessary to produce hair and continue its
  growth
• Follicular tag
• Hair pulled from the head
• Translucent tissue surrounding the hairs shaft
  near the root
• DNA analysis on follicular tag
• Hair individualized

HAIR FIBERS AND PAINT
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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
• Catagen transition phase (2-3 weeks), root is
  elongated
• Telogen phase where hair naturally falls out of
  the skin, root is club-shaped

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Hair Growth Cycle
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Hair Growth Cycle
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Hair Bulbs
Brushed-out hairs all have this kind of root
A normal telogen hair with a hard 'club' end,
seen under (left) light microscope and (right)
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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Comparing Strands

• Comparison microscope
• Match the color, length, and diameter.
• Distinguish human hair from the hair of animals
• Scale structure
• Medullary index
• Medullary shape

HAIR FIBERS AND PAINT
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Comparing Strands

• Other important features
• Presence or absence of medulla
• Distribution, shape, and color intensity of
  pigment granules present in the cortex
• Most common request
• Hair recovered at the crime scene hair removed
  from the suspect
• Subjective and highly dependant on the skills and
  integrity of the analyst

HAIR FIBERS AND PAINT
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Question Can the body area from which a hair
originated be determined?
Pubic Medulla
Pubic Hair Root
HAIR FIBERS AND PAINT
Pubic Hair
Beard Medulla
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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 damage
• Soft texture, pliable

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Limb Hairs

• Diameter fine with little variation
• Gross appearance of hair arc-like in shape
• Medulla is discontinuous to trace with a granular
  appearance

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Limb Hairs

• Soft texture
• Tips usually tapered, often blunt and abraded,
  rounded scale ends due to wear

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Pubic Hairs

Medulla relatively broad and usually continuous
when present
Root frequently with tag
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Pubic Hairs
Tip usually tapered, rounded, or abraded Stiff
texture, wiry
Shaft diameter coarse with wide variations and
buckling
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Facial Hairs (Beard/Mustache)

• Diameter very coarse with irregular or triangular
  cross-sectional shape
• Medulla very broad and continuous, may be doubled

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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
  appearance

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Chest Hairs

• Shaft diameter moderate and variable
• Tip often darker in color, long and fine,
  arc-like
• Medulla may be granular
• Stiff texture

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Other Body Hairs

• Eyebrow Stubby, some diameter fluctuation,
  saber-like in appearance
• Eyelash Short, stubby with little shaft diameter
  fluctuation, saber-like in appearance

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Question Can the racial origin of hair be
determined?
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Mongoloid Hair

• Shaft diameter coarse, usually with little or no
  variation
• Pigment granules densely distributed, often
  arranged in large patchy areas or streaks
• Medulla prominent (often broad and continuous)

HAIR FIBERS AND PAINT
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Negroid Hair

• Shaft diameter moderate to fine, considerable
  variation
• Pigment granules densely distributed (hair shaft
  may be opaque), arranged in prominent clumps
• Shaft prominent twist and curl
• Cross-sectional shape flattened

Negroid
HAIR FIBERS AND PAINT
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Caucasoid Hair

• Shaft diameter moderate with minimal variation
  (mean diameter for human head hairs - 80um)
• Pigment granules sparse to moderately dense with
  fairly even distribution
• Cross-sectional shape oval

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Question Can the age sex be determined from a
hair sample?
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Age Sex

• Only works for infant hair
• Fine
• Short in length
• Dye or bleach
• DNA testing to be certain

HAIR FIBERS AND PAINT
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Question Is it possible to determine if a hair
was forcibly removed from the body?
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Forcible Removal

• Tissue if pulled rapidly
• Less tissue if pulled slowly
  

Pulled Forcibly Removed Shed
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Question Are efforts being made to individualize
human hair?
HAIR FIBERS AND PAINT
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Individualization Of Human Hair

• Nuclear DNA from follicular tissue on root
• Absence of follicular tissue
• Extract DNA from hair itself
• Anagen phase best
• Mitochondrial DNA
• Extracted from hair shaft
• Outside nucleus
• Inherited from mother
• Many copies

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Individualization Of Human Hair

• Sometimes yes
• Used to exclude individuals
• Mitochondrial DNA cannot distinguish between
  people maternally related
• Microscopic analysis and DNA must match

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Animal v. Human Hair
Animal
Human
Medullary Index lt1/3 Medulla is absent for most
humans Medulla is continuous for Mongoloid race

• Medullary Index 1/2
• Medulla is present for all animals
• Medulla is continuous for most animals
• Medulla is patterned for most animals

Medulla is fragmented only some animals and
humans Medulla is cylindrical in shape (most
animals)
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Collection Preservation 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
• 50 full-length hairs from all areas of scalp
  representative sampling of head hair
• Two dozen full-length pubic hairs
• Victims of suspicious deaths during an autopsy

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Packaging of Hair Evidence

• Recover all hair present
• Use fingers or tweezers to pick up hair
• Place in paper bindles or coin envelopes
• Fold and seal in larger envelopes
• Label the outer sealed envelope

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Packaging of Hair Evidence

• Attached hair
• In dry blood, caught in metal or crack of glass,
  etc.
• Do not attempt to remove it
• Leave hair intact on the object
• Small object
• Mark
• Wrap
• Seal in an envelope
• Large object
• Wrap the area containing the hair
• Paper to prevent loss of hairs during shipment

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Fiber Evidence
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Types of Fibers Natural Fibers

• Derived in whole from animal or plant sources
• Wool
• Mohair
• Cashmere
• Furs
• Cotton
• Animal fibers hair
• Cotton most prevalent

HAIR FIBERS AND PAINT
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Natural Polymers
Figure 810  Starch and cellulose are natural
carbohydrate polymers consisting of a large
number of repeating units or monomers.
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Types of Fibers Man-made Fibers

• Manufactured
• Regenerated fibers
• Manufactured from natural raw materials
• Rayon, acetate, and triacetate
• Synthetic fibers
• Produced solely from synthetic chemicals
• Nylons, polyesters, and acrylics

HAIR FIBERS AND PAINT
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Types of Fibers Polymers

• Macromolecules
• Synthetic fibers
• Repeating units known as monomers

HAIR FIBERS AND PAINT
Figure 89  The chain-link model of a segment of
a polymer molecule. The actual molecule may
contain as many as several million monomer units
or links.
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Fiber Evidence

• Identify the origin of the fiber
• Or at least narrow the possibilities to a limited
  number of sources
• Fabrics that can be exactly fitted together at
  their torn edges fabrics were of common origin

HAIR FIBERS AND PAINT
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Fiber Evidence

• Microscopic comparisons between questioned and
  standard/reference fibers
• color and diameter characteristics
• comparison microscope

HAIR FIBERS AND PAINT
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Fiber Evidence

• Other morphological features for comparing fibers
  are
• Lengthwise striations on surface of fiber
• Presence of delustering particles that reduce
  shine
• Cross-sectional shape of the fiber

HAIR FIBERS AND PAINT
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Fiber Evidence

• Compositional differences
• Dyes that were applied to fibers during the
  manufacturing process
• Microspectrophotometer
• Chromatography of pigment
• Chemical composition of fibers
• Birefringence crystalline property of fiber

HAIR FIBERS AND PAINT
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Methods For Fiber Comparison

• Visible light microspectrophotometer
• Compare colors of fibers through spectral
  patterns.
• Chromatographic separation dye composition
• Generic class of fibers
• Infrared spectrophotometry
• Polarizing microscope characteristic index of
  refraction

HAIR FIBERS AND PAINT
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Collection and Preservation

• Investigators task
• Look for minute strands of fibers
• Identify and preserve potential carriers of
  fiber evidence
• Relevant articles of clothing
• Packaged carefully in separate paper bags
• If necessary to remove a fiber from an object
• Use clean forceps
• Place in a small sheet of paper
• Fold and label the paper
• Place the paper packet inside another container

HAIR FIBERS AND PAINT
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Paint Evidence
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Paint

• Paint spread onto a surface
• Dries into a hard film
• Pigments and additives suspended in the binder
• Common types of paint examined in the crime
  laboratory automobile finishes
• Variety of coatings to the body of an automobile
• Electrocoat primer
• Primer surfacer
• Basecoat
• Clearcoat

HAIR FIBERS AND PAINT
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Methods For Paint Comparison

• Wide diversity of automotive paint
• Contributes to forensic significance of
  automobile paint comparison.
• Questioned and known specimens
• Best compared side by side
• Stereoscopic microscope
• Color, surface texture, and color layer sequence

HAIR FIBERS AND PAINT
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Methods For Paint Comparison

• Pyrolysis gas chromatography
• Infrared spectrophotometry
• Identify the make and model of a car from a small
  amount of paint
• Use of color charts for automobile finishes

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Paint Pyrograms Of Acrylic Enamel Paints
Figure 821   (a) Paint from a Ford model and (b)
paint from a Chrysler model. Courtesy Varian
Inc., Palo Alto, Calif.
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Collection and Preservation

• Found on or near persons or objects involved in
  hit-and-run incidents
• Containers for paint
• Paper druggist folds
• Glass or plastic vials
• Paint smeared or embedded in garments or objects
• Whole item to be packaged
• Sent to the laboratory

HAIR FIBERS AND PAINT
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Collection and Preservation

• Uncontaminated standard/reference paint always
  collected
• Other items
• Tools used to gain entry into buildings
• Safes often contain traces of paint
• Tool collected, along with reference paint
  samples.

HAIR FIBERS AND PAINT
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Other Techniques

• Fluorescence microscopy
• Thin or bulk cross sections
• Aid in differentiating samples or various layers
• Within intact paint fragments
• Excitation wavelength of 365 nanometers
• Sensitive to differences in organic pigments,
  additives, and film-forming components
• Useful with light-colored architectural coatings

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Other Techniques

• Low-Temperature Ashing
• Oxygen plasma used to remove organic materials
  from a complex matrix
• Materials that produce volatile oxides
  (principally organic components)
• Removed from the matrix with minimal elevation of
  the sample temperature in contrast to pyrolysis
  systems
• Usually continues until all volatile oxides
  removed

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Other Techniques

• Inorganic pigments, extenders, and some additives
  in the different layers of the ashed paint film
• remain after the organic material is volatilized
• relative size and morphology of the different
  particles, noted during previous tests, serve to
  help identify and separate these residue
  components for additional analysis

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Other Techniques

• Analyzed by a variety of methods, including PLM,
  SEM-EDS, analytical electron microscopy (AEM), or
  XRD techniques

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Other Techniques

• Solvent Extraction
• Separates some of the organic components from
  paint films
• Recover a solute that can be examined by IR, GC,
  or GC-MS techniques
• Useful for coatings where the volume of pigments
  or extenders very high
• Identification of the binders by FTIR
• Only possible after separation of the pigments
  and extenders
• separation of paint layers important
• If impossible
• identical conditions (e.g., time, and
  temperature)
• applied to both the known and questioned samples

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Other Techniques

• Analytical electron microscopy
• Transmission electron microscopy (TEM)
• In conjunction with both selected area electron
  diffraction and EDS
• More definitive identification of some pigment
  grains
• AEM requires that
• Sufficiently thin to permit transmission of the
  analytical electron beam
• Applied only to dispersions of extracted
  inorganic particulates
• Those recovered from low-temperature ashing
• Dissolved paint layers
• Ultramicrotomed sections of a paint film

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FBI Hair Paper

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

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Summary