Trace Evidence, Hair, and Fibers

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Trace Evidence, Hair, and Fibers

• Coach Whitaker

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Vocabulary

• Trace evidenceis any small physical material
  that can be transferred from person to person or
  a crime scene
• Follicletubelike organ on the body that hair
  grows from
• Cuticleis the clear outside covering of the hair
  shaft
• Cortexcontains the pigment of hair strand and
  provides strength to the hair

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Vocabulary

• Medullainterior core of the hair and provides it
  flexibility
• Fibersare any threadlike element of a material
• Textilea fabric woven in a distinctive pattern
• Fabrica cloth material made up of fibers woven
  or bonded in a certain manner

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Trace Evidence

• Trace evidence is physical evidence found in
  small amounts at a crime scene
• Common examples are hair, fibers, paint chips,
  body fluids, stains, powders, explosive residue,
  glass particles, metals, and soil
• Trace evidence is any small material that can be
  transferred from person to person or a person and
  crime scene

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Trace Evidence

• Criminals are clever or they think they are
• Trace evidence creates links between suspects,
  places, and objects
• Trace evidence is often the only evidence that
  connects a person to a crime scene

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Trace Evidence

• An extremely important characteristic of trace
  evidence is its transferability
• It grabs and clings to clothing, hides in shoe
  seams, nestles in hair, and settles in nooks and
  crannies
• It survives for months or years

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Trace Evidence

• The analysis of trace evidence requires a
  thorough investigation of its physical and
  chemical properties
• Because most trace evidence is very small, it
  cannot be adequately examined with the naked eye

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Trace Evidence

• Equipment used to analyze TE
• Comparison Microscopeprovides a side by side
  comparison
• Mircospectrophotometrythe exact color of an
  object can be measured
• Polarized light microscopehelps objects appear
  more sharp and the colors are clearer
• Scanning Electron Microscopemagnifies an objects
  up to 100,000 times the original size
• Stereomicroscopehelps provide a FS a 3-D model
  of an object

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Equipment photos
Comparison Microscope
Mircospectrophotometry
Polarized light microscope
Stereomicroscope
Scanning Electron Microscope
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Activity

• Trace Evidence Collage
• Think of at least 15 pieces of trace evidence

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Hair

• Investigators often find hair at crime scenes
• Hair is considered class evidence and is useful
  in backing up circumstantial evidence (ex. Places
  someone at a scene)

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Hair

• The average human body has 5 million hairs
• Blond hair people have the most hair on their
  hand (120,000 strands) followed by Black and
  brown (100,000 strands) and Redheads (80,000
  strands)
• Hair is continuously shed and renewed at a rate
  of 100 each 24 hour period from the scrape alone

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Hair

• Hair is made up of complex-cross protein polymers
  that are resistant to breaking down
• It grows from a tubelike organ in the under layer
  of the skin called a hair follicle
• The root is embedded in the follicle and linked
  to the bodys blood supply

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Biology of Hair
Hair is composed of the protein keratin, which
is also the primary component of finger and toe
nails. Hair is produced from a structure called
the hair follicle. Humans develop hair follicles
during fetal development, and no new follicles
are produced after birth.
Hair color is mostly the result of pigments,
which are chemical compounds that reflect certain
wavelengths of visible light.
Hair shape (round or oval) and texture (curly or
straight) is influenced heavily by genes. The
physical appearance of hair can be affected by
nutritional status and intentional alteration
(heat curling, perms, straightening, etc.).
The body area (head, arm, leg, back, etc.) from
which a hair originated can be determined by the
samples length, shape, size, color, and other
physical characteristics.
In order to test hair evidence for DNA, the root
must be present.
Sources http//library.thinkquest.org/04oct/00206
/lesson.htmt_hair http//www.fbi.gov/hq/lab/fsc
/backissu/july2000/deedric1.htmIndex20(Hairs)
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Hair Structure
Hair is composed of three principal parts
Cuticle outer coating composed of overlapping
scales
The structure of hair has been compared to that
of a pencil with the medulla being the lead, the
cortex being the wood and the cuticle being the
paint on the outside.
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Hair Structure

• Cuticle
• The cuticle varies in
• Its scales,
• How many there are per centimeter,
• How much they overlap,
• Their overall shape, and
• How much they protrude from the surface
• Its thickness, and
• Whether or not it contains pigment.

Characteristics of the cuticle may be important
in distinguishing between hairs of different
species but are often not useful in
distinguishing between different people.
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Hair Structure

• Cortex
• The cortex varies in
• Thickness
• Texture
• Color
• Distribution of the cortex is perhaps the most
  important component in determining from which
  individual a human hair may have come.
• Microscopic examination can also reveal the
  condition and shape of the root and tip.

Info http//library.thinkquest.org/04oct/00206/le
sson.htmt_hair
Image http//www.extrapersonality.com/hair
.html
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Hair Structure

• Medulla
• The medulla may vary in
• Thickness
• Continuity - one continuous structure or broken
  into pieces
• Opacity - how much light is able to pass
  through it
• It may also be absent in some species.

http//library.thinkquest.org/04oct/00206/lesson.h
tmt_hair
http//www.bfro.net/images/whatis/figures/Fig.203
20with20caption.jpg
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Hair At The Crime Scene

• 1st the investigator must determine if the hair
  is animal or humans (root bulb-like or spear
  shape)
• Characteristics are studied
• Each person with hair have hairs with different
  characteristics and may have similarities
• Hairs strains may be different from the same
  person
• Things we learn from hair whether the source is
  animal or humans, racial origins (sometimes),
  location on the sources body

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Activity

• Hair Lab
• http//sciencespot.net/Pages/classforsci.htmlhair
  sfibers

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Fibers

• Fibers are any threadlike element of a material
  and are everywhere
• Because textiles are massed produced, it is
  difficult to trace it back to a specific source
  but it could create a link between victims,
  suspects, and places
• Statistics and probability play a big role
• Like hair, textile fibers are common items left
  at a crime scene

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Natural Fibers
Many different natural fibers that come from
plants and animals are used in the production of
fabric.
Cotton fibers are the plant fibers most commonly
used in textile materials
The animal fiber most frequently used in the
production of textile materials is wool, and the
most common wool fibers originate from sheep.
http//www.fireflydiapers.com/articles/diaperartic
le_naturalfibersabsorb.htm
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Synthetic Fibers
More than half of all fibers used in the
production of textile materials are synthetic or
man-made. Nylon, rayon, and polyester are all
examples of synthetic fibers.
Cross-section of a man-made fiber
Images http//www.trashforteaching.org/phpstore/p
roduct_images/YarnWS.JPG http//www.fbi.gov/hq/
lab/fsc/backissu/july2000/deedric3.htmFiber20Evi
dencehttp//www.jivepuppi.com/images/fiber_eviden
ce.jpg
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Fibers

• Fabrics are made from fibers
• Fibers are used to make textiles, such as cloth
  or carpeting rope, string, brushes, and filling
  materials

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Fibers

• Time is critical when collecting fibers because
  studies show fibers clinging to clothing are lost
  quickly
• After four hours, 80 of fibers have fallen away
  and after 24 hours, 95 may be gone
• Fibers can be lifted from clothing from tape or
  vaccuming
• At the crime scene, fibers can be found focal
  point of the crime

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Fibers

• Comparing fibers
• FS access fibers by assessing their diameters,
  shapes, colors, shininess, and curls and crimps,
  and then looking for any attached debris

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Activity

• Hair and Fiber ID
• http//sciencespot.net/Media/FrnsScience/hairfiber
  _IDlabwkst.pdf

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Class Project

• Classroom Crime Lab
• Hair and Class Crime