Forensics Hair, Paint, and Fibers

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

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• 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.

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

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• 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.

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• 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.

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• 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.

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• 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.

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• 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.

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• 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.

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• 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.

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

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• 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.

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• 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.

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• 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.

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• 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?
• 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

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• 11. Can the age and sex of an individual be
  determined from hair?
• Age can only be determined for infants.
• The recovery of DNA can prove male or female
  origin.

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

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• 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.

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

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

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• 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.

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• 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.
  

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• 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.

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

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• 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.

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• 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.

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• 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?

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• 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.

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• 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.

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

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• 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.

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

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• 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.

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• 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 can is probable.

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• 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.

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• 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.

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• 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.

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• 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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• 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.

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• 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.

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

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• 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

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• 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.

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• 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.

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• 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.