Chapter 3 The Study of Hair By the end of the chapter you will be able to:

Transcription

1 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 History of Hair Analysis One of first cases to use the investigation of hair was the murder of the Duchesse de Praelsin in Paris in 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 side byside, such as hair or fibers. Advances continue today with chemical tests, neutron activation analysis, and DNA 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 nonhuman each different hair sample must be in a separate envelope or paper bindle and must be labeled with its source. Due Monday Structure 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 environments 1

2 Structure 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 Structure of Hair continued 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 overlapping 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 hair 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 imbricate Types 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 medulla Types 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. Hair from different parts of the body 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 2

3 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 % 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 % are in this stage No pattern as to which hairs on the head are in a particular stage at any time Research 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 3 10 Animal 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 an animal, if it is 0.33 or less it is human hair. 3

4 Animal Hair and Human Hair Using Hair in an Investigation Spinous Coronal Imbricate The outermost layer of the hair shaft (the cuticle), is 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). Macroscopic investigation can indicate length, color, and curliness. Microscopic investigation can indicate fine detail in hair structure. pattern of medulla, pigmentation of cortex, types of scales, medullary index typical magnification is 40X 400X Specialized techniques Phase contrast microscopy observes fine detail. focuses light that passes through objects of different refractive indexes. shows more contrast when viewing translucent particles Fluorescence microscope filters to detect fluoresced light. beam of light of a certain color is used, if sample contains particular chemicals it will absorb some of the light and reemit light of a different color. can show Electron the presence microscopes of dye direct or other beam treatments. of electrons at a sample. provide more detail of the surface or interior (50,000X). In the sample below, note the overlapping scales and the pigment granules in the cortex. Testing for Substances in the Hair Shaft Chemicals that the skin absorbs often can be detected by analysis of the hair shaft. During testing hair is dissolved in an organic solvent that breaks down keratin and releases any substances that are in the hair. The hair shaft can be examined in sections to establish a timeline for exposure to toxins. Neutron Activation Analysis (NAA) can determine concentrations of substances in the sample. can identify 14 elements in a 2 cm strand hair placed in a nuclear reactor and elements will give off different gamma ray signals identifies antimony, argon, bromine, copper, gold, manganese, silver, sodium, and zinc probability of two individuals having the same concentration of 9 different elements is about one in a million. Useful if you don't have the follicle. Testing the Hair Follicle Microscopic assessment of the follicle is performed first because it is cost effective and quick. If a microscopic match is found between a suspect and a sample then the sample will be forwarded for blood and DNA testing If hair is forcibly removed and the entire hair follicle is present it is called follicular tag. (blood & tissue) The follicle can be blood tested and perhaps show the blood type. The follicle can also be DNA analyzed to provide identification with a high degree of confidence. 4

5 Summary Hair consists of a (a) hair shaft produced by a (b) follicle embedded in the skin. The shaft consists of an outer cuticle, a cortex, and an inner medulla. Various hair treatments produce characteristic effects useful to forensic experts. Some characteristics allow them to be grouped into general racial categories. Forensic experts examine hair using chemicals, light, electrons, neutrons, and DNA sequencing. Find 6 diseases that can cause changes in the hair. Describe each disease and what changes the hair undergoes, i.e how would you be able to tell the person has the disease by looking at the hair. 5