Forensics of Hair Analysis

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Forensics of Hair Analysis
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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

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Basic Hair Structure
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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

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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.

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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.

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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.

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Bat Hair and Mink Hair
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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.

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Medulla

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

Human
Animal
Deer
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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

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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.

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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.

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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.
  

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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.

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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.

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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.

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Forensic Identification

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

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• Caucasian
• African-American
• Mongoloid

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Where is this hair from?

• Certain features of individual hairs identify the
  region of the body where it originated.

Pubic Hair
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Where is this Hair from?
Limb
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Where is this hair from?
Beard
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There are also certain characteristics for

• Underarm hair
• Chest hair
• Eyebrow
• General body hair

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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.

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

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

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What is this?

• Lice

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