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Trace Evidence, Hair, and Fibers

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Trace Evidence, Hair, and Fibers Coach Whitaker Vocabulary Trace evidence is any small physical material that can be transferred from person to person or a crime ... – PowerPoint PPT presentation

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Title: Trace Evidence, Hair, and Fibers


1
Trace Evidence, Hair, and Fibers
  • Coach Whitaker

2
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

3
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

4
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

5
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

6
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

7
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

8
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

9
Equipment photos
Comparison Microscope
Mircospectrophotometry
Polarized light microscope
Stereomicroscope
Scanning Electron Microscope
10
Activity
  • Trace Evidence Collage
  • Think of at least 15 pieces of trace evidence

11
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)

12
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

13
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

14
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)
15
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.
16
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.
17
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
18
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
19
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

20
Activity
  • Hair Lab
  • http//sciencespot.net/Pages/classforsci.htmlhair
    sfibers

21
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

22
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
23
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
24
Fibers
  • Fabrics are made from fibers
  • Fibers are used to make textiles, such as cloth
    or carpeting rope, string, brushes, and filling
    materials

25
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

26
Fibers
  • Comparing fibers
  • FS access fibers by assessing their diameters,
    shapes, colors, shininess, and curls and crimps,
    and then looking for any attached debris

27
Activity
  • Hair and Fiber ID
  • http//sciencespot.net/Media/FrnsScience/hairfiber
    _IDlabwkst.pdf

28
Class Project
  • Classroom Crime Lab
  • Hair and Class Crime
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