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Forensics of Hair Analysis

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helpful in demonstrating physical contact with a suspect. Until recently, the comparison microscope was considered the ... Bat Hair and Mink Hair. Human Hair ... – PowerPoint PPT presentation

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Title: Forensics of Hair Analysis


1
Forensics of Hair Analysis
2
Hair Forensics
  • One of the most common is hair evidence.
  • helpful in demonstrating physical contact with a
    suspect
  • Until recently, the comparison microscope was
    considered the only reliable tool for the
    identification and comparison of the microscopic
    characteristics found in hair
  • Today, nuclear and mitochondrial DNA (mtDNA)
    testing can provide additional information that
    can influence the value of microscopic
    examinations

3
Basic Hair Structure
4
Hair Facts
  • A hair grows from the papilla and with the
    exception of that point of generation is made up
    of dead, cornified cells
  • It consists of a shaft that projects above the
    skin, and a root that is imbedded in the skin

5
Hair
  • Its basic components are keratin (a protein),
    melanin (a pigment), and trace quantities of
    metallic elements.
  • These elements are deposited in the hair during
    its growth and/or absorbed by the hair from an
    external environment.
  • After a period of growth, the hair remains in the
    follicle in a resting stage to eventually be
    sloughed from the body.

6
Hair Cuticle
  • The cuticle is a translucent outer layer of the
    hair shaft consisting of scales that cover the
    shaft. Cuticular scales always point from the
    proximal or root end of the hair to the distal or
    tip end of the hair.

7
Cuticle
  • There are three basic scale structures that make
    up the cuticlecoronal (crown-like), spinous
    (petal-like), and imbricate (flattened).
  • Combinations and variations of these types are
    possible.

8
Bat Hair and Mink Hair
9
Human Hair
  • The imbricate or flattened scales type consists
    of overlapping scales with narrow margins.
  • They are commonly found in human hairs and many
    animal hairs.

10
Medulla
  • The medulla is a central core of cells that may
    be present in the hair.

Human
Animal
Deer
11
Medulla
  • The medulla, when present in human hairs, is
    generally less than one-third the overall
    diameter of the hair shaft.
  • The medulla in animal hairs is normally
    continuous and structured and generally occupies
    an area of greater than one-third the overall
    diameter of the hair shaft.
  • There are many more characteristics of hair that
    are too numerous to discuss for the purpose of
    this lab

12
Animal Versus Human Hairs
  • Human hairs are generally consistent in color
    and pigmentation throughout the length of the
    hair shaft, whereas animal hairs may exhibit
    radical color changes in a short distance, called
    banding.
  • The pigmentation of human hairs is evenly
    distributed, or slightly more dense toward the
    cuticle, whereas the pigmentation of animal hairs
    is more centrally distributed, although more
    dense toward the medulla.

13
Hair Forensics
  • Hairs found on a knife or club may support a
    murder and/or assault weapon claim.
  • A questioned hair specimen can be compared
    microscopically with hairs from a known
    individual, side-by-side.
  • Human hairs can be classified by racial origin
    such as Caucasian (European origin),
    African-American (African origin), and Mongoloid
    (Asian origin).
  • In some instances, the racial characteristics
    exhibited are not clearly defined, indicating the
    hair may be of mixed-racial origin.

14
Hair Forensics
  • The region of the body where a hair originated
    can be determined with considerable accuracy by
    its gross appearance and microscopic
    characteristics.
  • The length and color can be determined.
  • It can also be determined whether the hair was
    forcibly removed, damaged by burning or crushing,
    or artificially treated by dyeing or bleaching.

15
Hair Forensics DNA
  • Often it is not possible to extract DNA fully, or
    there is not enough tissue present to conduct an
    examination.
  • Hairs with large roots and tissue are promising
    sources of nuclear DNA. However, DNA examinations
    destroy hairs, eliminating the possibility of
    further microscopic examination.

16
Hair Forensics Collection
  • Hairs can be recovered from items using a number
    of different techniques.
  • Some of the methods used to collect hairs from
    clothing and bedding items are scraping, shaking,
    taping, and picking.
  • Debris from large carpeted surfaces might be
    vacuumed into a filtered canister.
  • If the specific location of a hair on a clothing
    item is important, it might be necessary to pick
    off the hair or tape the item and record where
    the hair was removed.

17
Hair Forensics Which Hairs?
  • Head hairs and pubic hairs exhibit a greater
    range of microscopic characteristics than other
    human hairs therefore, head and pubic hairs are
    routinely forensically compared.
  • Twenty-five randomly selected head hairs are
    generally considered adequate to represent the
    range of hair characteristics of that individual.
  • It is recommended that the same number of hairs
    be collected from the pubic region.

18
Forensic Identification
  • Human hairs can generally be identified by racial
    origin, body area, and other comparison
    characteristics.
  • Racial indicators apply primarily to head hairs.

19
  • Caucasian
  • African-American
  • Mongoloid

20
Where is this hair from?
  • Certain features of individual hairs identify the
    region of the body where it originated.

Pubic Hair
21
Where is this Hair from?
Limb
22
Where is this hair from?
Beard
23
There are also certain characteristics for
  • Underarm hair
  • Chest hair
  • Eyebrow
  • General body hair

24
Things to consider when viewing hair
  • Length Length is considered, although hairs may
    have been cut between the time of deposition of
    the questioned specimen and the collection of a
    known sample. In addition, there may be a
    significant difference in the lengths of the
    shortest and longest hairs on an individual's
    head. Tip The tip can be cut, broken, split,
    abraded (rounded), or finely pointed as
    illustrated by An individual's grooming, hygiene,
    health, and nutrition can affect these features.

25
  • Glass-Cut or Broken Hair Tip
  • Cut Hair Tip
  • Worn Razor-Cut Tip

26
Dyed hairs possess an unnatural cast or color. In
addition, the cuticle will take on the color of
the dye
27
  • Scissor Cut
  • Razor Cut
  • Broken Hair
  • Burned Hair

28
What is this?
LICE
29
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