The Study of Hair - Weebly

The Study of Hair - Weebly

The Study of Hair Ms Clark, 2014 PVMHS Hair evidence What information can be gained from analysis of hair? Hair alone (without follicle cells) is trace evidence & class evidence. It does not identify a specific individual, but can narrow your suspects down

based of certain characteristics of their hair. Hair evidence Hair is easily left behind at a crime scene. Adheres easily to carpet, clothes, and many other surfaces (sheets, blankets, car interior, moist surfaces). Hair has a tough outer coating and does not decompose easily, so its durable.

Hair can be analyzed to determine race, history of drug use, evidence poisoning/toxins, nutritional deficiencies. Hair analysis can sometimes indicate what water supply a person is using! History of Hair Analysis 1883: Alfred Swaine Taylor and Thomas Stevenson publish The Principles and Practice of Medical Jurisprudence and include a chapter on using hair in

forensic investigations. 1910: Victor Balthazar & Marcell Lambert (French forensic scientists) publish Le Poil de lHomme et des Animaux (the hair of man and animals) which includes microscopic studies of hair from most mammals. 1934: Dr. Sydney Smith uses a comparison microscope to perform side-by-side analysis of hairs collected from a crime scene. Today hair analysis includes neutron activation analysis (NAA) , chemical analysis, and DNA analysis

The Function of Hair Why do mammals (including humans) have hair? The Function of Hair Helps to regulate body temperature What happens when you get cold? Why? Protects the skin against sunlight Acts as a sensory organ When hair is very dense, its called fur.

The Structure of Hair Hair originates from the skin. Your skin is known as the Integumentary system. Hair is an accessory organ to your skin. The skin has 3 layers: Epidermis (most superficial layer, at the surface)

Dermis (middle layer) Hypodermis (deepest layer) The Structure of Hair Hair originates from the hair bulb, is surrounded by the hair follicle, and is located in the dermis. The end of the follicle is called the papilla, this is where the blood vessels meet the

hair to supply nutrients. The Structure of Hair (Generally) a sebaceous gland (oil gland) is associated with each hair bulb. Helps water proof the hair and protect it from drying out. A muscle that attaches to the

hair follicle to erect the hair when stimulated (cold or scared). The hair shaft is what you see (the hair on your arm or on your head). The Structure of Hair The cuticle of the hair is composed of keratin, a protein produced in the skin.

Proteins are made up of chains of amino acids that are connected by strong bonds, making hair strong and flexible. The Structure of Hair The hair shaft is made up of 3 layers: the medulla, the cortex, and the outer cuticle. Pencil analogy:

-Central medulla -Cortex surrounds medulla -Cuticle on outside The Cuticle The outer layer of the hair shaft, made up of keratin. The scales point away from the scalp. This can indicate where the

younger part of the hair is (closest to the scalp). Useful when looking for drugs or toxins at a specific point in time. The Cuticle Humans have scales that are flattened and narrow, called imbricate scales. Some animals have hair with different scales, this allows

scientists to distinguish human hair from animal hair. Coronal scales have the appearance of a stack of crowns. Spinous scales resemble petals. Imbricate - Human Coronal - rodents Spinous - cats

The Cortex Contains most of the pigment granules, called melanin. This gives the hair its color. Pigment distribution varies from person to person Some people have larger pigment granules, giving a more uneven distribution when viewed under a microscope. The Medulla

The center of the hair is called the medulla. There are different patterns that a person could have Continuous Interrupted Fragmented/segmented

Solid Absent There is also significant differences between species. Medulla patterns Variation in Hair Shape: hair may be circular, triangular,

flattened, or irregular. Length Color: depends on distribution of pigment granules. Human hair is usually one color along the entire length unless it has been artificially dyed. Animals often have pigments found in solid masses called ovoid bodies, this is why the color of animal hair can appear banded.

Variation in Hair Texture: Vibrissa the whiskers of many animals Bristle coarse hair that provides a protective coat Wool fine hairs that cover the bodies of mammals and protect from wet & cold Diameter: The ratio of the diameter of the medulla to the diameter of the hair is

called the medullary index. Animals have a greater medullary index than humans. Human Hair Head and body hair of humans is intermediate combining the characteristics of bristle and wool. 4 types: Primordial hairs appears in 3rd month of gestation Lanugo hairs replaces the primordial hairs,

appears around the 5th month of gestation and are generally shed by the 8th month of gestation. Vellus hairs soft hairs spread uniformly all over the body Terminal hair found on the scalp, eyebrows/eyelashes, limbs/body, pubic, & axillary regions. Life Cycle of Hair Hair proceeds through 3 stages as it develops. Anagen stage: Period of active growth when cells

around the follicle are rapidly dividing. Lasts 2-6 years on the scalp, but may be less on other areas of the body. Canagen stage: Period of transition, hair follicle shrinks & papilla detaches Telogen phase: Follicle remains dormant, eventually hair will loosen and fall out and the anagen stage begins again. Hair as evidence

Review Locards exchange principle Whenever 2 objects come in contact, some transfer of material will occur. Hair is trace evidence Hair can be collected by plucking, shaking, placing tape over a surface, using a special vacuum. If a large number of hairs are collected from a crime scene the technician has to compare the hairs from the crime scene to hairs from

the victim and/or suspect. Hair analysis Can be analyzed macroscopically and microscopically. Macroscopic analyses include length, color, texture, curliness. Microscopic analyses include medulla pattern, cortex pigmentation, type of scales on the cuticle, and medullary index.

Hair analysis Many dyes will fluoresce under certain types of light. Chemical tests can be used to determine presence of toxins or drugs. If hair is forcibly removed the hair follicle may be present. This is known as a follicular tag. Blood and tissue attached to the tag may be analyzed for blood type and

DNA analysis. Chemical analysis By testing different parts of the hair its possible to establish a timeline for when exposure to poisons or other toxins occurred. Chemical analysis Hair grows about 1.3 cm per

month if a toxin occurs at 9cm from the root, you would divide by 1.3 to get the approximate time that the exposure occurred. Chemical analysis Neutron Activation Analysis (NAA) can be used to identify up to 14 elements in a single 2cm strand of hair.

Including: antimony, argon, bromine, copper, gold, manganese, silver, sodium, arsenic, chlorine, and zinc The probability of 2 hairs having the same profile is very low. Any questions?

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