Chapter 3
The Study of Hair
By the end of the chapter you will be able to: • identify the various parts of a hair • describe variations in the structure of the medulla, cortex, and cuticle • distinguish between human and nonhuman hair • determine if two examples of hair are likely to be from the same person • explain how hair can be used in a forensic investigation • calculate the medullary index for a hair
Hair is considered class evidence
blonde hair would exclude people with Asian and African ancestry (can determine if hair has been dyed) secondary transfer : hair can adhere to clothes, carpet or other surfaces and then be transferred to other locations. Common with animal hair does not easily decompose because of tough outer covering physical characteristics give clues of racial background chemical tests can provide information about drug use, toxins, heavy metals, nutritional deficiencies only if follicle is attached, can it provide DNA, which would be individual evidence • One of first cases to use the investigation of hair was the murder of the Duchesse de Praelsin in Paris in 1847. • A.S.Taylor and T. Stevenson, in 1883, wrote a forensic science text that included a chapter on hair. • V. Balthazard and M. Lambert, in 1910, published a comprehensive study of hair. • Dr. Sydney Smith, in 1934, first used a comparison microscope to analyze hairs side by side. comparison microscope compound microscope that allows scientists to examine samples sideby side, such as hair or fibers. • Advances continue today with chemical tests, neutron activation analysis, and DNA analysis.History of Hair Analysis
Function of Hair
• Hair on mammals helps to 1) regulate body temperature, 2) decrease friction, 3) protect against sunlight and 4) act as a sense organ. Fur is simply dense hair. • In humans, the temperature regulation function is reduced by the lack of hair compared to many other mammals (goose bumps) 1. Terms Quiz Monday secondary transfer cortex comparison microscope cuticle hair shaft melanin hair follicle imbricate papilla neutron activation analysis sebaceous gland Taylor & Stevenson keratin Balthazard & Lambert medulla Dr. Sydney Smith 2. Collect 5 different hair samples human and non human each different hair sample must be in a separate envelope or paper bindle and must be labeled with its source. Due MondayStructure of Hair
• Hair consists of a hair shaft produced by a follicle embedded in the skin. follicle: the actively growing root or base of a hair containing DNA and living cells club shaped papilla: network of blood vessels at the end of the follicle that supply nutrients to the hair sebaceous gland: secretes oil to help keep the hair conditioned nerve cells wind around the follicle and stimulate muscles in response to changing environmentsStructure of Hair continued
• hair shaft is composed of the protein keratin, produced in the skin, which makes it strong & flexible keratin: type of fibrous protein that makes up the majority of the cortex of a hair keratin made of amino acid chain in helix shape• A hair has three layers: the inner medulla, the cortex, and the outer cuticle. (Analagous to a pencil)
Cuticle is the tough outermost layer made of over lapping scales that protect the inner layers of the hair. Cortex is the thickest layer, surrounding the medulla, containing granules of pigment which give hair its color. distribution of pigment in the cortex varies from person to person. pigment, commonly, is denser nearer the cuticle. melanin: bits of pigment found in the cortex of a hairStructure of Hair continued
The Cuticle
transparent scales point from proximal end (nearest skin) to the distal end can determine older and younger ends of hair useful when analyzing hair for the presence of different toxins, drugs, etc In humans, scales are flattened and narrow and are also called imbricateTypes of Medulla
Medulla (inner section) can be hollow or filled with cells Patterns: absent, interrupted (intermittent), fragmented (segmented), continuous, or solid It may or may not contain pigment. Hair may contain a double medullaTypes of Hair
Buckled Blunt Double Medulla
• The cross section of a hair can be circular, triangular, irregular, or flattened influencing the curl of the hair. • Texture of a hair can be coarse or fine. • Different hairs from one location on a person can vary can have just some gray hairs 50 hairs are usually taken from a suspect's head and, if necessary, 25 hairs from the pubic region. • Different regions of the body on which hair can vary are (1) head, (2) eyebrows and lashes, (3) mustache and beard, (4) underarms, (5) overall body (auxiliary hair), and (6) pubic. Cross sections differ 1. head hair is circular or elliptical 2. eyebrows and eyelashes are circular with tapered ends 3. mustache/beard are thick and triangular 4. body/pubic hair is oval or triangular arm & leg hair tend to have blunt ends and could be frayed from abrasion beard hair is coarse and may have double medulla buckling may be present in pubic hair
Hair from different parts
of the body
The Life Cycle of Hair
Hair proceeds through 3 stages as it develops: • During the long anagen stage (~1000 days), hair actively grows. The cells around the follicle rapidly divide and deposit materials in the hair. 8090% of all human hair is in this stage • In the catagen stage, the hair grows and changes. ~2% of all hair growth and development • Hair is in the telogen stage when the follicle becomes dormant. During this stage, hairs easily can be lost. 1018% are in this stage • No pattern as to which hairs on the head are in a particular stage at any timeResearch a case (not in your book) in
which hair is an important piece of
evidence.
1. Summary of case
2. Other evidence
3. How hair was used
Treated Hair
• Bleaching disturbs the scales on the cuticle and removes pigment leaving hair brittle and a yellowish color. artificial shows sharp demarcation while sun bleaching shows a more gradual mark • Dyeing colors both the cuticle and sometimes the cortex of the hair shaft. dye is recognizable as unnatural to experienced forensic scientists • Hair grows on average 1.3 cm per month (.44 mm/day) measuring the length of hair and dividing by 1.3 cm provides you with an approximation of the # of months since the hair was colored. • Because of this and because hair grows daily, a person’s treated hairs will have specific characteristics in common with her or his lost hairs.Racial
Differences
• Hair examiners have identified some physical characteristics that can be associated with broad, racial groups. • These characteristics, however, will not apply to all individuals in these groups. • In addition, at times, it will be impossible to assign specific hairs to any of these groups because their characteristics are poorly defined or hard to measure. • See Figure 310Animal Hair and Human Hair
• animal hair pigment is denser toward the medulla. In humans it is denser toward the cuticle. • animal pigments are often in solid masses called ovoid bodies, especially in dogs and cattle • Unlike human hair, animal hair can abruptly change colors in banded patterns along the length of hair. • The medullary index in animals is much thicker. medullary index: ratio of diameter of the medulla to the diameter of the entire hair if index is 0.5 or greater, the hair came from anAnimal Hair and Human Hair
Spinous Coronal
The outermost layer of the hair shaft (the cuticle), isImbricate
typically different in animals and humans. • The cuticle scales in animals (cats, seals, and mink) tend to resemble petals (spinous) or they give the appearance of a stack of crowns (coronal), like in rodents and bats. • The cuticle scales in humans commonly are flattened and narrow (imbricate).
