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Unit 5 Hair and Fiber Analysis

Unit 5 Hair and Fiber Analysis

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Unit 5 Hair and Fiber Analysis

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  1. Unit 5 Hair and Fiber Analysis Students will examine hair and fibers in relation to physical evidence.

  2. Unit 5 Vocabulary • Hair shaft • Hair cuticle • Hair cortex • Hair medulla • Coronal scales • Spinousscales • Imbricate scales • Hair root • Hair follicle • Anagen phase • Catagen phase • Telogen phase • Plain weave • Twill weave • Satin weave • Knitted weave • Synthetic fiber

  3. Obj 1A: Microscopic Structure of Hair A. Shaft – portion of hair above the surface of the skin, made up of three layers 1. Cuticle – clear outside covering of the shaft, made up of overlapping scales. There are three basic scale structures that make up the cuticle. Combinations and variations of these types are possible. Corona-crown-like, found in small rodents and bats, rarely in humans Spinous- petal-like, found in seals, cats, & some animals never humans Imbricate-flattened, found in humans and animals

  4. Obj. 1A: Microscopic Structure of Hair 2. Cortex – made up of keratin molecules, the pigment that gives hair its color. 3. Medulla – row of cells running along the center of the cortex which may appear dark or translucent depending on the presence of air, liquid, or pigment. Can be fragmentary, interrupted, continuous, or stacked. May not be visible in human hair. In animals, it is at least 1/3 of the diameter of the hair.

  5. Medullary Index is the quickest way to determine a hairs origin in terms of human or non-human. • Hair is 3-D & of a circular nature • A circumference is the distance across a circle • If the circumference of the medulla is less than 1/3 (33%) the circumference of the entire shaft, then it is most likely of human origin. • If the circumference of the medulla is greater than 1/3 (33%) of the circumference of the entire shaft, then it is most likely of animal origin.

  6. Medualla diameter vs. total diameter = medullary index

  7. Moose hair: medullary index is > 1/3

  8. Pigment granules

  9. Obj. 1A: Microscopic Structure of Hair B. Root – portion of hair below the skin, embedded in the follicle C. Follicle – tube like organ in the under layer of the dermis and is linked to the body’s blood supply 1. Papilla – indentation of follicle where blood vessels, nerves enter and exit 2. Matrix – area of cell division and hair growth

  10. Obj. 1B: GENERAL BIOLOGICAL MAKE-UP OF HAIR • A. Shapes of hair 1. Round = Straight Hair 2. Oval – curly hair 3. Crescent – kinky hair • B. Growth 1. There are 3 stages a. Anagen phase – active phase, averaging three to five years for scalp, 30-45 days for other parts of the body, hair grows about 1 cm a month. b. Catagen phase- intermediate period of hair growth, lasting 2-3 weeks, outer sheath shrinks to the root forming club hair, 3% of all hair at any one time c. Telogen phase –resting phase, 10-15% of all hair, lasts about 100 days for scalp and longer for other parts of the body, club hair fully formed.

  11. Obj. 1B: General Function of Hair • C. Function 1. Protection a. guards the scalp from injury and sunlight b. eyebrows and eyelashes protect the eye c. hair in ears and nostrils keep out foreign objects 2. Helps regulate body temperature 3. Touch receptors associated with hair follicles

  12. Obj. 1C: CHEMICAL ABSORPTION • A. Hair Root • 1. Materials that enter the body are transported to the hair root through the blood vessels and deposited into the cortex. • 2. Since hair grows slowly, drug use can be traced over longer periods of time compared to blood and urine. • 3. Analyzing lengths of hair can indicate continuous or infrequent use and can even be matched to an approximate time line. • 4. There has been some success in scientists identifying metal poisoning through the examination of the cortex

  13. Obj. 1C: CHEMICAL ABSORPTION • B. Scalp oil • 1. Sometimes investigators can find traces of a person’s environment in scalp oil. Examples – smoke from crack cocaine or heavy metal industrial pollutants. • 2. False positives are possible if the person was present where there were environmental factors.

  14. Obj. 1D. HAIR! Humans & animals • A. Human race differences – risky to assign racial characteristics, but some generalizations can be made 1. European Origin a. Shaft diameter: moderate with minimal variation (mean diameter for human head hairs - 80um) b. Pigment granules: sparse to moderately dense with fairly even distribution c. Cross-sectional shape: oval 2. African Origin a. Shaft diameter: moderate to fine with considerable variation b. Pigment granules: densely distributed (hair shaft may be opaque) and arranged in prominent clumps c. Shaft: prominent twist and curl d. Cross-sectional shape: flattened

  15. Obj. 1D. HAIR! Humans & animals 3. Asian Origin a. Shaft diameter: coarse and usually with little or no variation b. Pigment granules: densely distributed and often arranged in large patchy areas or streaks c. Medulla: prominent (often broad and continuous) d. Cuticle: thick e. Cross-sectional shape: round

  16. Obj. 1D. HAIR! Humans & animals • B. Root differences 1. Mature hair – bulblike shape with few if any pigment granules 2. Mature hair pulled from scalp – may have follicular tissue attached and may looked stretched and there may be pigment granules since the hair was still growing 3. Animal roots – generally spear shaped

  17. Obj. 1D. HAIR! Humans & animals • C. Pigmentation differences between human and animals 1. 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 distribution and density of pigment in animal hairs can also be identifiable features. 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, and more dense toward the medulla.

  18. HAIR SAMPLES FROM DIFFERENT HUMAN RACES AND ANIMALS • • (from basic structure to scale casts) •

  19. Obj. 2 A: IDENTIFY AND COMPARE NATURAL AND SYNTHETIC FIBER • A. Microscopic Examination 1. Natural fibers have variation in shape, twisting, edges which are not smooth or scale patterns (wool), etc. a. cotton – flattened tubes, twisted and bent b. silk – tubular, doesn’t twist much c. wool – looks like animal hair, overlapping scales d. Linen – plant fiber 2. Synthetic fiber – smooth forms, uniform shapes along the entire strand. The shapes are produced by machines.

  20. Most Common Fibers • Natural = cotton • Synthetic = polyester

  21. Obj. 2A: IDENTIFY AND COMPARE NATURAL AND SYNTHETIC FIBER • B. Chemical testing methods 1. Most current fiber analysis, like paint, is done with a Fourier Transform Infrared Spectrometer (FTIR).

  22. Obj. 2A: IDENTIFY AND COMPARE NATURAL AND SYNTHETIC FIBER • 2. Fibers can also be tested with the following: • Burn tests: The way a fiber burns can indicate the fiber type. The smell released when burned (such as wool) or the way it burn completely or melts, etc. • Thermal decomposition: this burn test uses the smoke produced to determine its origins. It uses red and blue litmus paper, as well as lead acetate filter paper. • Acid tests, base tests, acetone tests: These tests are used to determine what type of fibers the warp and the wefts are made of. Different types of fibers may dissolve or turn colors in the presence of the different chemicals.

  23. Obj. 2B: COMPARE AND CONTRAST COMMON FIBER WEAVE PATTERNS • Woven fabrics are made by interlacing warp and weft yarns, forming threads and textiles. • Plain – simplest and most common, warp and weft pass under each other alternately, design resembles a checkerboard • Twill – pass the warp yarn over one to three weft yarns before going under one, makes a diagonal weave, design resembles stair steps, denim is a good example • Satin – yarn interlacing is not uniform, creates long floats, interlacing weave passes over four or more yarns, satin is a good example • Knitted – interlocking loops into a specific arrangement, may be one continuous thread or a combination, yarn is formed into successive rows of loops then drawn through another series of loops

  24. Obj. 2C: PROCEDURES FOR COLLECTION AND ID OF HAIR AND FIBER EVIDENCE • Recovery of evidence should be the most direct but least intrusive technique • Bag clothing item individually in paper bags, make sure that different items are not placed on the same surface before being bagged • Make tape lifts of exposed skin areas of bodies and any inanimate objects • Removed fibers should be folded into a small sheet of paper and stored in a paper bag