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H air Forensic

H air Forensic

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H air Forensic

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  1. Hair Forensic

  2. Objectives :1. Introduction 2. Hair structure3. Hair growth4. Difference between human and animal hair5.collection and preservation6. Examination 7. Hair Toxicology

  3. 1. Introduction: Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the crime. From hair, one can determine: 1. If the source is human or animal 2. Race (sometimes) 3. Origin of the location on the source’s body 4. Whether the hair was forcibly removed 5.If the hair has been treated with chemicals 6. If drugs have been ingested

  4. Biology of Hair Hair is composed of the protein keratin, which is also the primary component of finger and toe nails. Hair is produced from a structure called the hair follicle. Humans develophair follicles during fetal development, and no new follicles are produced after birth. Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light. Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc.). The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample’s length, shape, size, color, and other physical characteristics. In order to test hair evidence for nuclear DNA, the root must be present. The hair may also be tested using mitochondrial DNA whether or not the root is present. Sources: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair & http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Index%20(Hairs)

  5. Skin Structure

  6. Hair Shaft • Composed of: • Cuticle—outside covering, made of overlapping scales • Cortex—inner layer made of keratin and embedded with pigment; also contains air sacs called cortical fusi • Medulla—inside layer running down the center of the cortex

  7. Cuticle : The cuticle is the outermost layer of hair which is covered with scales. The scales point toward the tip of the hair. Scales differ among species of animals and are named based on their appearance. The three basic patterns are:

  8. Human Scales ; In order to visualize the scales: Paint clear fingernail polish on a glass slide. When the polish begins to dry, place a hair on the polish. When it is almost dry, lift off the hair and observe the scale imprints.

  9. Cortex : • The cortex gives the hair its shape. • It has two major characteristics: • Melanin—pigment granules that give hair its color • Cortical fusi—air spaces, usually found near the root but may be found throughout the hair shaft

  10. Medulla : The medulla is the hair core that is not always visible. The medulla comes in different types and patterns. Types: Intermittent or interrupted Fragmented Continuous Stacked Absent—not present

  11. Medulla Human Animal Deer

  12. Human medulla may be continuous, fragmented, or absent.

  13. Medullary Index Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair. Medullary index for human hair is generally less than 1/3. For animal hair, it is usually greater than 1/2.

  14. Hair Shape Can be straight, curly, or kinky, depending on the cross-section, which may be round, oval, or crescent-shaped. Crescent moon (Kinky) Oval (Curly) Round (Straight)

  15. Hair Growth Anagen—hair is actively growing; lasts up to 5 years Catagen—hair is not growing; a resting phase Telogen—follicle is getting ready to push the hair out; lasts two to six months Grows about 0.4 mm per day, or 1 cm per month; approximately one-half inch per month

  16. Hair Growth • Growth cycle has three distinct phases • Hair can stay on head for approx. 6 years • If forcefully pulled out and in one of first two phases, follicle tissue will likely be found with the hair follicle (right) Diagram showing the three phases of hair growth

  17. Root ;’ Human roots look different based on whether they have been forcibly removed or they are telogen hairs and have fallen out. Animal roots vary, but in general have a spear shape. Fallen out Forcibly removed

  18. Human hairs can be classified by racial origin such as Caucasian (European origin), African-American (African origin), and Mongoloid (Asian origin).

  19. Hair from different races Negroid Mongoloid Caucasoid

  20. Animal Versus Human Hairs Human hairs are generally consistent in color and pigmentation throughout the length of the hair shaft, whereas animal hairs may exhibit radical color changes in a short distance, called banding. • The pigmentation of human hairs is evenly distributed, or slightly more dense toward the cuticle, whereas the pigmentation of animal hairs is more centrally distributed, although more dense toward the medulla.

  21. Collection of Hair Questioned hairs must be accompanied by an adequate number of control samples. • From victim • From possible suspects • From others who may have deposited hair at the scene Control sample • 50 full-length hairs from all areas of scalp • 24 full-length pubic hairs

  22. Instrument : Microscopy -stereomicroscop -Polarizes microscope -Fluorescence Microscope -Comparision microscope-SEM -Infrared microspectroscopy Pyrolysis GC(cosmetic treatment ) Biochemical method-enzyme typing(esterase,phosphoglucomutase Isoelectri focusing in polyacrylamide gel for noncarboxymethylated keratin useful in spsdeermination

  23. Examination : Color Length Diameter Distribution, shape, and color intensity of pigment granules • Dyed hair has color in cuticle and cortex • Bleaching removes pigment and gives a yellow tint Scale types Presence or absence of medulla Medullary index

  24. Scissor Cut • Razor Cut • Broken Hair • Burned Hair

  25. Dyed hairs possess an unnatural cast or color. In addition, the cuticle will take on the color of the dye

  26. DNA from Hair The root contains nuclear DNA. If the hair has been forcibly removed, some follicular tissue containing DNA may be attached. The hair shaft contains abundant mitochondrial DNA, inherited only from the mother. It can be typed by comparing relatives if no DNA from the body is available. This process is more difficult and more costly than using nuclear DNA.