Forensics: ch3 Hair Analysis

History of hair Analysis

- 1883: Alfred Saint Taylor and Thomas Stevenson covered hair in forensic science - 1910: Victor Balthazard and Marcella Lambert published a comprehensive study of hair - 1934: Dr. Sydney Smith, analyzed hairs side by side using a comparison microscope - Today: Standard procedures of hair analysis include microscopic examination and DNA analysis.

How can investigators use hair left at a crime scene as evidence?

- A hair w/out the follicle and its nuclear DNA, or genetic material in its nucleus, cannot provide individual evidence. Physical examination of the hair can only yield class evidence. - Hair left behind at a crime scene can where to clothes, carpets, and many other surfaces and be transferred to other locations. This is called secondary transfer, and it is particularly common with animal hair (Locards Principle of Exchange) - because of its tough outer coating, hair does not easily decompose. Hair found at crime scenes or secondary locations can be analyzed. The physical characteristics of hair can offer clues to the predominant ancestry of an individual.

Collecting Hair in an Investigation

- According to Locard's Principle of Exchange two objects that come into contact will transfer materials. The presence of a suspects hair at a crime scene does not prove his or her guilt because you cannot prove when it was left there. - Hair can be collected from the crime scene, suspect(s), or the victim by plucking, shaking, and scraping surfaces. It can also be collected by placing tape over the surface so that the hair adheres to it. When surfaces are large, they can be vacuumed. - Forensic investigators must search all elements of the crime scene for hair, including vehicles; the fingernails, and hands of the victim; or in the body (during autopsy); blood or other body fluids of the victim or suspect; weapons, tape, or ligatures; abandoned clothing or masks; explosive device mechanisms.

Functions of Hair

- All (and only) mammals have hair. It's main purpose is to regulate body temperature to keep warm through insulation. - Hair also decreases friction, protects the skin against sunlight, and acts as a sense organ. - The dense hair of some mammals is referred to as fur. - Hair works as temperature regulator in association with muscles in the skin. If the outside temperature is cold, these muscles pull the hair strands upright, creating pocket that trap air. This trapped air provides a warm, insulating layer next to the skin. If the temperature outside is warm, the muscles relax, and the hair becomes flattened against the body, releasing the trapped air. - humans are born with about 5 million hair follicles, only 2% of which are on the head. As a human ages, the density of hair decreases

Animal hair and Human hair

- Animal and Human hair haver several differences, including the pattern or pigmentation, the medullary index, and the cuticle type. - Pigmentation in human hair tends to be denser towards the cuticle, in animals it is denser towards the medulla. In animal hair, pigments are often found in solid masses called Ovoid Bodies, especially in dogs and cattle. Human hairs are usually one color along the length. - In other animals, the medulla is proportionally much thicker than it is in humans. This air-filled region of a hair aids in providing insulation. The ration of the diameter of the medulla to the diameter of the entire hair is known as the Medullary Index. - The cuticle of the shaft of the hair can also help distinguish human hair from other animal hair. Rodents and bats have a Coronal Cuticle with scales that look like a stack of crowns. - Cats, seals, and mink have scales that are called Spinous and resemble petals. - Human hair has cuticle scales that are flattened and narrow, which are called Imbricate.

Treated hair

- Bleaching hair oxidizes the natural pigment, lightening it. It also makes hair brittle and can disturb the scales on the cuticle. - Artificial bleaching shows a sharp demarcation along the hair, while bleaching from the sun leaves a more gradual mark. - Peroxide in bleach can also damage mtDNA. Dyeing hair changes the color of the hair shaft and gives it a painted appearance that is easily recognized by an experienced forensic examiner. In addition, he cuticle and cortex both take on the color of the dye. - If an entire hair is recovered in an investigation, it it possible to estimate when the hair was last color-treated. The region near the root of the hair will be colored naturally. Human hair grows at a rate of 1.3cm/month. Measuring the length of the hair that is naturally colored and dividing by 1.3cm provides an estimate of the number of months since the hair was colored.

How does chemical testing assist in evidence analysis?

- Chemical tests preformed on hair, such as gas chromatography, can identify and quantify drugs, toxins, heavy metals, and even assess nutritional deficiencies. - When the follicle or even a portion of the shaft of a hair is present, DNA evidence may be obtained from it, which may lead to individual identification.

Hair from different parts of the body

- Forensic scientists distinguish 6 types of hair on the human body: head hair, eyebrows and eyelashes, beard and mustache hair, underarm hair, body hair, and pubic hair. - Hair types have has its own shape and characteristics - Head hair is generally circular but often have tapering ends - Beard hairs tend to be thick and triangular. Usually coarse and may have double medulla. - Body hair can be elliptical or triangular, depending on whether the body region has been regularly shaved. Arm and legs usually has a blunt tip, but may be frayed at trends from abrasion - Pubic hair tends to be oval or try. The diameter of pubic hair may vary greatly, and buckling, abrupt changes in the shape of the hair shaft, may be present.

Mitochondrial DNA (mtDNA)

- Genetic material in the mitochondria of the cytoplasm of a cell, only inherited from the mother. - Present in the hair shafts, can reveal some of a suspect's or victim's family relationships.

Types of hair

- Hair can very in shape, length, diameter, texture and color. - The cross section of the hair maybe circular, triangular, irregular, or flattened. Influencing the curl of the hair. - The texture of hair can be coarse as it it on whiskers or fine as it id on younger children. - hair color varies depending on the distribution of pigment granules and on hair dyes that might have been used. - In humans, hair varies from person to person. In addition, different hairs from one part of a persons body can vary. Not all hairs on a persons head are exactly the same. Because inconsistencies occur within each body region, 50 hairs are usually collected from a suspect's or victim's head.

Ethnic or Ancestral Differences

- Hair examiners have identified some key physical characteristics that are associated w/ hair of different general ancestor all groups -European, Asian and Africa. - European: generally straight or wavy, small and evenly distributed (pigment granules); oval or round of moderate diameter w/ minimal variation (cross section); color may be blond, red, brown, or black. - Asian: Straight, densely distributed (pigment granules); round w/ large diameter (cross section); shaft tends to be coarse and straight; thick cuticle; continuous medulla; color black. - African: Kinky, curly, or coiled; shaft may be buckled; densely distributed, clumped, may differ in size and shape (pigment granules); flattened with moderate to small diameter and considerable variation (cross section)

Microscopy

- Length, color, and curliness are macroscopic characteristics. - If many hairs are collected, an investigator compares the sample with hair taken from the six major body regions of the victim/suspect. - An initial analysis is performed using a low-power compound microscope to determine whether the hair is human or nonhuman. - Microscopic characteristics include the pattern of the medulla, pigmentation of the cortex, and types of scales on the cuticle. Medullary Index is calculated. Typical magnification for viewing hair is between 40-400 magnification.

Chemical testing for substances in the hair shaft

- One method of identifying drugs or toxins involves dissolving the hair in an organic solvent that breaks down the hair protein, thereby releasing any substances incorporated into the hair. - Scientists have devised a sort of tracking system for suspects or victims that uses isotope analysis of a strand of hair. This technique involves determining the ratio of different forms of certain elements in a person's hair and body tissues. By using isotope analysis, a single strand of hair can provide a timeline of a person's movements. - Through chemical and radiological analysis of a single strand of hair, information that includes a person's travels, their diet, and their drug intake and toxin exposure may be revealed. Knowing this information may provide essential clues to investigators trying to solve a crime.

The structure of human hair

- The hair follicle is a club shaped structure in the skin. It contains cells with DNA along with a network of blood cells that supply nutrients to feed the hair and help it grow. Human hair consists of a follicle, a shaft, and a tip The follicle (with papilla and capillary blood supply) of the hair contains the nuclear DNA, which is used to identify individuals - The shaft is composed of the protein, called keratin - Epidermis is the outer layer of skin, inner layer dermis - Sebaceous gland (oil gland) to help condition the scalp - Papilla the part of the root that has the blood supply - The hair shaft is made up of three layers: an inner medulla, a cortex, and an outer cuticle -The cuticle is the transparent outer layer of the hair shaft. It is made up of overlapping scales. - Human hair has imbricate scales, narrow and flat. - The cortex is the largest part of the hair shaft. It contains melanin, the pigment that gives the color to the hair.

Several types of microscopic techniques

1. Phase contrast: involves using a special objective lens and special condenser with a compound microscope. This configuration focuses light that passes through objects at different angles. The resulting image shows more contrast, especially when viewing translucent particles. Phase contrast microscopy is useful for observing fine detail in hair structure. 2. Fluorescence microscope: a beam of light of a certain wavelength is used. If the sample contains particular chemicals, it will absorb some of the light and them re-emit light of a different wavelength. This is called Fluorescence. A Fluorescence microscope is equipped w/ filters to detect the fluoresced light, indicating the presence of a dye or other treatment. 3. Electron microscope: Instead of using light to view a sample, electron microscopes direct a beam of electrons at a sample. Electron microscopes provide remarkably detailed views of a sample, magnifying is 50,000 times or more.

Comparison microscope

A compound microscope that allows side-by-side comparision of samples, such as hair or fibers

Gas chromatography

A method of separating chemicals to establish their quantities

Nuclear DNA

Genetic material in the nucleus of a cell

The life cycle of hair

Hair proceeds develop in 3 stages: 1. Anagen Stage: and lasts approximately 1,000 day. 80-90% of all human hair is in the anagen stage. This is the period of active growth when the cells around the follicle are rapidly dividing and depositing materials within the hair. 2. Catagen Stage: follows as the har stops growing and the follicle recedes as the blood supply is reduced. The catagen stage accounts for about 2% or all hair growth and development. 3. Telogen Stage: during this stage, the hair follicle is dormant or resting and hairs are easily lost. About 10-18% of all hairs are in the telogen stage. At the end of the telogen stage, the blood supply reconnects to the follicle, and another anagen phase begins.

Hair follicle

The actively growing base of a hair that contains DNA and living cells

Types of medulla

The center of the hair is called the medulla. It can be a hollow tube. In some people the medulla is absent, in others it is fragmented, or segmented, and in others it is continuous or even doubled. The Medulla can contain pigment granules or be unpigmented.

Medulla

The central core of a hair

Hair shaft

The part of the hair above the follicle, contains mitochondrial DNA

Cortex

The region of hair located outside the medulla that contains grandules of pigment

Cuticle

The tough outer covering of a hair that is composed of overlapping scales

Keratin

The type of fibrous protein that makes up the majority of the cortex of a hair