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Hair,%20Paint,%20and%20Fiber%20Evidence

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Title: Hair,%20Paint,%20and%20Fiber%20Evidence


1
Hair, Paint, and Fiber Evidence
2
  • A. Morphology of hair
  • 1. HAIR IS AN APPENDAGE OF THE SKIN THAT GROWS
    OUT OF AN ORGAN KNOWN AS A HAIR FOLLICLE.

3
  • 2. The length of hair extends from its root or
    bulb embedded in the follicle, continues into a
    shaft, and terminates at the tip end.

4
  • 3. The shaft is composed of three layers that
    forensic scientist are most interested in.
  • The cuticle, cortex, and medulla.

5
  • 4. The cuticle is the outer layer of the hair. It
    is composed of overlapping scales that always
    point toward the tip end of the hair. These
    scales make the hair resistant to decomposition
    and help it retain its structural features for
    long periods of time.

6
  • Hair by itself cannot be identified to a single
    person but it can be used to identify animal
    species because of the differences in scales.

7
  • 5. The layer underneath the cuticle is the
    cortex. It is the main body of the hair shaft.
    Its most important forensic aspect is that it is
    embedded with pigment granules that give its
    color. This helps with comparison.

8
  • 6. Medulla is a cellular column running through
    the center of the hair. In some animals this
    column takes up a large part of the hairs
    diameter. This is known as the medullary index.

9
  • In humans it is 1/3. The presence and appearance
    of the medulla varies greatly.
  • Some have a continuous medulla.
  • Some have interrupted medulla.
  • Some have fragmented medulla.

10
  • Most human head hair have no medulla. If present
    it is usually fragmented. Except the Mongolian
    race who have continuous medulla.
  • There is a searchable database available which
    examines hair based on scale patterns and medulla
    type.

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  • 7. Roots the root and other surrounding cells
    contained within the hair follicle provide the
    tools necessary to produce hair and continue its
    growth.
  • There are three phases of hair growth.

13
  • Anagen 1st phase, may last up to six years. The
    hair follicle is attached to the root. If the
    hair is pulled out with the root attached it will
    contain a follicular tag. These are important for
    doing DNA analysis.

14
  • Catagen 2nd phase. Hair continues to grow but
    at a slower rate. Lasts about 2 to 6 weeks.

15
  • Telogen the final stage. Hair growth has
    stopped. During a 2 6 week period the hair will
    be pushed out of the follicle and shed.

16
  • 8. Identification and comparison of hair
  • The crime lab will be asked to identify which
    species the hair came from or if the hair came
    from another individual involved in the crime.

17
  • A comparison microscope is used for this task.
  • They may be able to identify chemicals on the
    hair or when the hair was last dyed.
  • Hair grows at an average of I cm per month. Other
    factors learned from examination include disease,
    infection, or drug use.

18
  • 9. Can the body area from which a hair originated
    be determined? Yes, by looking at pigmentation,
    courseness, diameter and tips.

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  • 10. Can the racial origin of hair be determined?

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  • Usually

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  • African Caucasian
  • Pigment is Very fine to
  • dense and coarse pigments
  • unevenly distributed evenly distributed
  • Flat to oval Oval cross-
  • cross-section section

23
  • 11. Can the age and sex of an individual be
    determined from hair?

24
  • Age can only be determined for infants.
  • The recovery of DNA can prove male or female
    origin.

25
  • 12. Is it possible to determine if a hair was
    forcibly removed from the body?

26
  • A hair root that has follicular tissue adhering
    to it is indicative of a hair that has been
    pulled out. Hair that falls out naturally will
    have a root free of tissue. However, hair that is
    pulled out slowly is less likely to have root
    tissue that hair pulled out quickly.

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  • B. Fibers
  • 1. Natural fibers are derived in whole from
    animal or plant sources. Animal fibers account
    for the majority of natural fibers encountered in
    the crime lab.

29
  • These include hair coverings such as wool,
    mohair, cashmere, mink, etc. The procedure for
    analyzing these is basically the same as that for
    hair.

30
  • The most common plant fiber is cotton.
    Unfortunately the wide use of this makes it hard
    to use as evidence.

31
  • 2. Man-made fibers. These are fibers derived from
    either natural or synthetic polymers. The fibers
    are typically made by forcing the polymer
    material through the hole of a spinneret.

32
  • Most of the fibers currently manufactured are
    produced solely from synthetic chemicals and are
    therefore classified as synthetic fibers.
    Examples include nylon, polyester, and acrylics.

33
  • 3. The polymer is the basic chemical substance of
    all synthetic fibers. Polymers are long-chained
    molecules. Examples of things manufactured from
    polymers are plastics, paints, adhesives, and
    rubber.

34
  • 4. The first step in analysis of a fiber is
    microscopic comparison for color, shape, and size
    using a comparison microscope.

35
  • The second step would be to analyze the dye or
    dyes present on the fibers.
  • The last phase of comparison is to determine if
    two fibers are chemically identical.

36
  • C Forensic Examination of Paint.
  • 1. One of the most commonly encountered types of
    physical evidence, most frequently in hit-and-run
    and burglary cases. Usually the forensic
    scientist will be asked to compare two or more
    paints for the purpose of determining common
    origin.

37
  • 2. The paint from an automobile can be used to
    determine the color, make, and model of a car.
  • 3. What is paint made of?

38
  • Paint is composed of pigments (to give color and
    hiding quality) and a binder which provides the
    support medium for the pigment and other
    additives. The binder is usually a polymer.

39
  • 4. Automotive paint there are four basic
    coatings for auto paint.
  • a. The ELECTROCOAT PRIMER is the first layer. It
    is electroplated onto the steel body to provide
    corrosion resistance. Usually grey or black in
    color.

40
  • b. The PRIMER SURFACER is applied over the
    electrocoat primer. Its function is to smooth out
    and hide seams or imperfections.
  • Color differs.

41
  • c. The BASECOAT is the layer that provides the
    color and appearance of the finish. Mica
    pigments, aluminum flakes, and other materials
    are added to give paint an individual and unique
    appearance.

42
  • d. The CLEARCOAT has no color and is used to
    provide gloss and add durability.

43
  • The microscope has traditionally been and remains
    the most important instrument for locating and
    comparing paint specimens.
  • Color imparts paint with its most distinctive
    forensic characteristics.

44
  • The importance of layer structure for evaluating
    the evidential significance of paint is very
    important.
  • When paint specimens posses colored layers that
    match with respect to number and sequence of
    colors a common origin is probable.

45
  • The diverse chemical composition of paint can
    provide for additional points of comparison
    between specimens.
  • A thorough comparison of paint must include a
    chemical analysis of either the paints pigment,
    binder, or both.

46
  • Pyrolysis gas chromatography is a valuable and
    accepted technique for distinguishing most paint
    formulations. In this process paint chips as
    small as 20 micrograms are decomposed by heat
    into numerous gas products.

47
  • These products are sent through a gas
    chromatograph. What emerges and is recorded are
    the separated decomposition products of the
    polymer used in the paint.

48
  • It is the pattern of this chromatogen or
    pyrogram that distinguishes one polymer from
    another. What results is a pyrogram that is
    sufficiently detailed enough to reflect the
    chemical make-up of the binder.

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50
  • Infrared spectrophotometry is another analytical
    technique used to provide information about the
    binder composition of paint. Binders will
    selectively absorb infrared radiation to yield a
    spectrum that is highly characteristic of a paint
    specimen.

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  • The elements that comprise the inorganic pigments
    of paint can be identified by either emission
    spectroscopy, neutron activation analysis, X-ray
    diffraction, and X-ray spectroscopy. The emission
    spectrograph can simultaneously detect 15 to 20
    elements in most automobile paint.

53
  • Crime labs are often asked to identify the make
    and model of a car from a very small amount of
    paint left behind at a crime scene.
  • Color charts for automobile finishes are
    available from paint manufacturers.

54
  • Starting in 1974 the Law Enforcement Standards
    Laboratory has collected and given out to crime
    labs auto paint samples from domestic passenger
    cars.

55
  • The data collected from crime scenes can be
    compared to data in the Paint Data Query Database
    to determine possible make, model and year of the
    paint.

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  • End

57
  • DRUGS

58
  • Unit 9 Drugs
  • 1. A drug can be defined as a natural or
    synthetic substance that is used to produce
    physiological or psychological effects in humans
    or other higher order animals.

59
  • 2.
  • a. Drug dependence exists in numerous patterns
    and in all degrees of intensity depending on
    several factors.
  • There are two types of dependence psychological
    dependence and physical dependence.

60
  • b. Physical dependence drug abuse is caused by
    an underlying psychological need and the desire
    to fulfill them.
  • Ex. To escape reality, relief from personal
    problems, stress.
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