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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 • Spinous • Imbricate • Hair root • Hair follicle • Hair papilla • Hair matrix • Anagen phase • Catagen phase • Telogen phase • Plain weave • Twill weave • Satin weave • Knitted weave • Synthetic fiber

  3. Forensics book pages 78-79 Read the case study. Based on your current knowledge, who are the best candidates for suspects?

  4. 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—coronal (crown-like, found in small rodents and bats, rarely in humans), spinous (petal-like, found in seals, cats, & some animals never humans), and imbricate (flattened, found in humans and animals). Combinations and variations of these types are possible.

  5. 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.

  6. 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

  7. Hair: Physical or Class Evidence? • Unless DNA is obtained, hair is considered to be class evidence • Nuclear DNA can be obtain from hair if a follicle is attached. Hair that is forcibly pulled out is more likely to have useable nuclear DNA. • Mitochondrial DNA can be found in the shaft of the hair. This DNA links families together through the female line. mtDNA will typically be class evidence since it identifies a family, but not a specific person. Enough circumstantial evidence can still give a conviction.

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. HAIR SAMPLES FROM DIFFERENT HUMAN RACES AND 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

  13. HAIR SAMPLES FROM DIFFERENT HUMAN RACES AND 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

  14. HAIR SAMPLES FROM DIFFERENT HUMAN RACES AND 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

  15. HAIR SAMPLES FROM DIFFERENT HUMAN RACES AND 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, although more dense toward the medulla.

  16. HAIR SAMPLES FROM DIFFERENT HUMAN RACES AND ANIMALS • http://www.fbi.gov/hq/lab/fsc/backissu/july2004/research/2004_03_research02.htm • (from basic structure to scale casts) • http://www.fbi.gov/news/stories/2005/march/hair031605/?searchterm=hair

  17. Book work • Forensics book: • Read pages 88-89 • Complete the assessment on page 90, except #1

  18. IDENTIFY AND COMPARE NATURAL AND SYNTHETIC FIBER • A. Physical testing methods 1. Natural fiber 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 – Cross sections are different depending on the nozzle used when the fibers are extruded. Can included round, trilobal, dogbone or dumbbell, 4-lobed, octalobal, irregular, multi-lobed or serrate. Because of the nature of production, synthetic fibers maintain a consistent shape

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

  20. 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). This uses a beam of light to determine the molecular groups present in a sample. First the fiber is flattened with a small rolling pin and then transferred to the salt window. Once there, the beam of light can be focused on the fiber and a graph with peaks and valleys will appear on the computer screen. Synthetic fibers are wonderfully uniform (compared to natural fibers).

  21. COMPARE AND CONTRAST COMMON FIBER WEAVE PATTERNS • Woven fabrics are made by interlacing warp and weft yarns. • 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

  22. Book Work • Forensics book pgs 100 – read & do the lab • Forensics book pgs 101-102 – read & do the lab • Forensics book pg 109, 110, 111, 118 – do each lab, each on its own lab notebook page


  24. 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

  25. CAREERS IN HAIR & FIBER ANAYLSIS • For each career listed, find the following information: • Levels of education required • Credentialing requirements • Employment opportunities • Workplace environments • Career growth potential • A. Forensic Chemist • B. Forensics Fiber Expert • C. Computer Forensics

  26. Hair & Fiber Review • Vocabulary! Use each vocabulary word in an appropriate sentence. • Draw and label a piece of hair • Draw and label a follicle • Describe how to tell the difference between a human hair and an animal hair • Know the different stages of hair growth – summarize each • What type of DNA is found in different parts of the hair • Know different examples of natural and synthetic fibers, know the most common types