Hair Evidence

• Forensic chemistry & toxicology


  The study of chemical evidence in criminal investigations
• Hair


  • One of the oldest forms of physical evidence
  • Available because the hair of each kind of animal is different and distinct for all others
  • Most crimes cause contact between one person to another and there maybe transfer of fibers and hairs
  • Successful investigation of crimes of violence are frequently materially assisted by the result of examination of hair and fibers
• Hair structure


  • Specialized epithelial outgrowth of the skin which occur everywhere on the human body except on the palm of the hands, the sole of the feet, lips, tip of the penis, clitoris, and labia minora
  • Hair is not completely round but may be oval or flattened
  • Very resistant to decomposition and putrefaction; thus, they often remain as a means of identification
• Class evidence from hair

  • Physical characteristics of hair can offer clues to the broad racial backgrounds of an individual
  • Chemical tests can provide a history of drug use, presence of heavy metals, and nutritional deficiencies
  • When the follicle of hair is present, DNA evidence may be obtained
• Two kinds of hair (mammals)

  • Real hair - generally long and stiff
  • Fuzz hair - generally short, fine at times, curly and wooly
• Parts of the hair

  • Root - portion embedded in the skin; provides for growth of old and new hair
  • Shaft - portion above surface of the skin and the most distinctive part of the hair
  • Tip - sometimes termed as pointed and distal end of an uncut hair shaft
• Two kinds of roots

  • Living roots - often found on hair in full growth
  • Dry roots - dead roots
• Three phases of hair growth


  1. Anagen phase - growing phase ("on" phase); lasts for approximately 1000 days; phase when hair multiplies rapidly

  2. Catagen phase - regressive phase, hair stops growing, lasts for only 1 to 2 weeks

  3. Telogen phase - final phase ("off" phase), towards the end a new hair in the anagen phase develops and forces the old telogen hair, lasts for about 5 to 6 weeks
• Follicular tag


  Importance for forensic analysis: tells you if the hair has fallen out or pulled out
• Nuclear DNA from hair

  Follicular tag is a useful source of DNA
• Microscopic parts of the hair shaft

  • Cuticle - outermost covering of the hair
  • Cortex - intermediate and the thickest layer of the shaft
  • Medulla (aka core) - central canal of the hair that may be empty or may contain various sorts of cells
• Medulla

  • Continuous in large number of animals
  • Interrupted in humans, monkeys and horses
• Medullary index (M.I.)


  Relationship between the diameter of the medulla and the diameter of the whole hair, usually expressed in fractions
• Comparison of medullary index between human and animal hair

  • Human - M.I. less than 0.5, medulla may not be present, scale pattern is fine and each overlaps the other more than 4/5, pigment granules are fine
  • Animal - M.I. more than 0.5, medulla is always present, scale is course and overlaps less than 1/2, pigment granules are course
• Characteristics by race


  • Negroid (African) - contain heavy pigment distributed unevenly, thin cross section is oval, hair is usually kinky
  • Mongoloid (Asian) - hair contains dense pigment distributed more evenly, cross section is round to oval, hair is coarse and straight with heavy black medulla
  • Caucasian (European) - hair contains very fine to coarse pigment distributed more evenly, cross section is oval to round, usually straight or wavy
• Characteristics by sex


  Male - generally larger in diameter, shorter in length, more wiry in texture

  Female - if a hair is as much as 6 inches in length and has split ends

  
  

  Note: Sex cannot be definitely determined from hair examination.
• Somatic origin - region of the body from which the human hair has been removed


  • Scalp hair - more mature, longest, uniform diameter

  Pubic hair - coarse and wiry, buckling diameter, continuous to discontinuous medulla, tapered but sometimes abraded or cut tips

  Vulvar - secondary pubic hair, finer and shorter than pubic hair, maybe abraded

  Chest hair - moderate to considerable diameter variation, long fine arch-like tip usually longer than pubic hair

  Facial hair - beard or moustache, coarse, can have a triangular cross section, blunted or razor cut tip

  Axillary hair - armpit hair, blunt tip, abraded or frayed, usually straighter than pubic hair, sometimes yellow and bleached

  Eyebrow - 1 cm long, curved, relatively coarse for length, smooth curved with punctuated tip and large medulla

  Eyelash - less than 1 cm long, short curved pointed hair

  Limb - shorter in length, arch-like in shape and often abraded or tapered at the tips

  Ear - pinna, downy

  Buttock - anal hair, short abraded hair

  Nose hair - similar to facial hair

  Fringe hair - neck, sideburns, abdomen, upper leg, back
• Age (approximate)

  Cannot be determined from hair examination with any degree of certainty except in infant hairs

  Infant hairs are fine, short in length, have fine pigment and are rudimentary in character

  Children's hair through adolescence is generally finer and more immature than adult hair but cannot be definitely differentiated with certainty

  Pigment is missing or starting to disappear in hair from adults

  Prematurely gray hair in young persons is common but NOT body hairs
• Questioned hairs can be collected using tweezers and placed in clean envelopes, or using adhesive tape to lift from suspected articles.
• Sample hairs can be collected through the following means:

  1. Combing or brushing
  2. Pulling - Pulled out hairs are the best samples (presence of root)
  3. Clippings - Least satisfactory method and should be adopted only when hair is clipped as close to the skin as possible.
• Collection of Hair Samples

  When questioned hairs are submitted to a forensic laboratory for examination, they must always be accompanied by an adequate number of control samples from the victim, from the crime scene, and from individual suspected of having deposited hair at the crime scene.
• Collection of Hair Samples

  Collection of control hair is carried out by taking a representative sampling of hair from the different parts of the body.
• Collection of Hair Samples

  As a general rule, forensic hair comparisons involve either the head hairs or pubic hairs. The collection of 50 full length head hairs from all areas of the scalp will normally ensure a representative sampling of head hairs. Likewise, a dozen of hairs from the pubic region.
• Collection of Hair Samples

  In rape cases, care must first be taken to comb the pubic area with a clean comb to remove all loose foreign hair present before the victim is sampled for control hair. The comb should then be packed in a separate envelope.
• Collection of Hair Samples

  In case of suspicious death, hair samples should be collected before the autopsy.
• Collection, Packaging, Preservation, and Transportation

  All of the hair in the questioned specimen should be submitted but do not mix hair at different places.
• Collection, Packaging, Preservation, and Transportation

  In vicious assault and murder cases, obtain clothing of the victim from the hospital or morgue to avoid the loss of evidence by careless handling and to prevent the clothing to be destroyed.
• Collection, Packaging, Preservation, and Transportation

  Representative samples of hair from the victim as well as the suspect should be obtained if possible. To be a representative head hair samples from a particular individual, it should consist of at least a dozen hairs from and preferably full length hair.
• Collection, Packaging, Preservation, and Transportation

  Don’t mix known samples of hair from different parts of the body.
• Collection, Packaging, Preservation, and Transportation

  The hairs should be placed in a folded paper or in a white mailing envelope, but the corners of the envelope should be sealed with a scotch tape.
• Collection, Packaging, Preservation, and Transportation

  Do not secure the hair samples to a piece of paper with a scotch tape because this will damage the hair.
• Collection, Packaging, Preservation, and Transportation

  All foreign fibers should be removed from the submitted specimens.
• Collection, Packaging, Preservation, and Transportation

  Fragmentary hairs or underdeveloped hairs are not suitable for examination.
• Collection, Packaging, Preservation, and Transportation

  Areas on an object containing hairs should be protected with cellophane or paper tape over the area before wrapping the object from transmittal laboratory.
• Melanin

  • the brownish-black pigment of the hair
  • responsible for the color of the hair
• Hair Color

  1. White - lacks melanin (albinism)
  2. Gray Hair - a mix of pigmented and unpigmented hair
  3. Black and Brown - tons of melanin
  4. Blond - less melanin
  5. Red Hair - contains an extra pigment called trichosiderin (iron based)
• Width of Hair

  17 micrometer to 181 micrometer
• Character of the Hair Tip if present

  • Tips of body hairs become rounded from rubbing against the cloth.
  • Human hair usually shows a fine tip.
  • Men's hair tip is apt to be cutoff square.

  Note: Hair tip characteristic may show whether a hair has been cut or not.
• Presence of Dye in Hair

  • Dyed hair has a dull appearance and color tone is constant.
  • Individual pigment granules of undyed hair stand more shaped.
  • If there has been subsequent growth of the hair since dyeing, the undyed root end portion will stand out markedly.
• Determination of whether naturally or artificially curled

  An altered hair will still have the natural shape of its follicle when view under microscope. Straight hair have a round follicle shape; wavy hair have an oval follicle shape; and curly hair have an elliptical follicle shape.