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Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
Forensics:hair, fiber, and paints
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Forensics:hair, fiber, and paints

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  • 1. Hairs, Fibers, and Paint Chapter 8
  • 2. Dermis <ul><li>Contains </li></ul><ul><ul><li>smooth muscle </li></ul></ul><ul><ul><li>blood vessels </li></ul></ul><ul><ul><li>nerve tissue </li></ul></ul><ul><ul><li>hair follicles (accessory organ of skin) </li></ul></ul><ul><ul><li>sweat glands (accessory organ of skin) </li></ul></ul><ul><ul><li>sebaceous glands (accessory organ of skin) </li></ul></ul><ul><li>Contains nerve receptors – to sense light/heavy touch or pressure </li></ul><ul><li>Contains connective tissue made of collagen and elastic fibers </li></ul>
  • 3. Full-thickness Skin
  • 4. Accessory Organs of the Skin <ul><li>Hair follicles </li></ul><ul><li>Nails </li></ul><ul><li>Skin glands </li></ul><ul><ul><li>Sebaceous glands </li></ul></ul><ul><ul><li>Sweat glands (a.k.a sudoriferous glands) </li></ul></ul><ul><ul><ul><li>Eccrine </li></ul></ul></ul><ul><ul><ul><li>Apocrine </li></ul></ul></ul>
  • 5. Hair Follicles <ul><li>Follicles are present on all skin excepts palms, soles, lips, nipples </li></ul><ul><li>In some areas that grow hair, the hair may be fine, while in others it may be thick </li></ul><ul><li>A hair grows out of a deep tube that extends from the surface of the skin, all the way into the dermal layer – this is a follicle </li></ul><ul><li>Each hair follicle is also connected to sebaceous glands that produce oils and other secretions </li></ul>
  • 6. Hair Follicle, cont’d. <ul><li>The follicle contains the growing hair shaft </li></ul><ul><li>The base of the hair is composed of actively dividing epidermal cells </li></ul><ul><li>These epidermal cells are nourished by dermal blood vessels near the hair base – this area at the base of the hair follicle is called the hair papilla </li></ul>
  • 7. Morphology and Structure of Hair
  • 8. Hair Morphology Con’t
  • 9. Morphology: Cuticle <ul><li>Protective coating made of overlapping scales, produce a characteristic pattern </li></ul><ul><li>Scales always point toward tip of hair </li></ul><ul><li>Not useful in individualizing human hair </li></ul><ul><li>Can be used for species identification </li></ul>
  • 10.  
  • 11. Morphology: Cortex <ul><li>Embedded with pigment granules that give hair its color </li></ul><ul><li>The color, shape and distribution of the granules provide points for forensic comparison </li></ul>
  • 12. Morphology: Medulla <ul><li>canal like structure of cells that runs through the center of the cortex </li></ul>
  • 13. Medullary Index <ul><li>Measure of the diameter of the medulla relative to the diameter of the hair shaft </li></ul><ul><li>Usually expressed as a fraction </li></ul><ul><li>Humans: medullary index < 1/3 </li></ul><ul><li>Animals: medullary index > 1/2 </li></ul>
  • 14. Medullary Index: How to figure it out…
  • 15. Medulla of Different Species
  • 16. Medulla Patterns <ul><li>Uniserial -small blocks in a row </li></ul><ul><li>Multiserial - several rows of blocks across a hair diameter </li></ul>
  • 17. <ul><li>Vacuolated – Uneven pattern </li></ul><ul><li>Lattice -circular pattern </li></ul>
  • 18. Forensic Analysis of Medulla <ul><li>Presence of medulla varies quite a bit: even hair to hair </li></ul><ul><li>Human head hairs generally have no medulla or may be fragmented ones; except Mongoloid race whose medulla is usually continuous </li></ul><ul><li>Most animals have medulla that is continuous or interrupted </li></ul><ul><li>The shape of the medulla can help identify a species </li></ul><ul><li>Examples: </li></ul><ul><ul><ul><li>Most animals and humans: cylindrical </li></ul></ul></ul><ul><ul><ul><li>Cats: pearl shape </li></ul></ul></ul><ul><ul><ul><li>Deer: spherical occupying whole hair shaft </li></ul></ul></ul>
  • 19. Identification and Comparison of Hair <ul><li>Morphological Characteristics do not allow individualization of a human hair to any single head or body </li></ul><ul><li>Hair when collected with an adequate number of standards/references can provide strong circumstantial evidence </li></ul><ul><li>Scale structure, medullary index, and medullary shape are most often used for hair comparison </li></ul><ul><li>Evidential value lies with degree of probability associated with a questioned hair and an particular individual </li></ul><ul><li>11 percent of all morphological hair matches are generally found to be non-matches—meaning microscopic hair comparisons are presumptive in nature—must be confirmed by DNA comparisons </li></ul>
  • 20. Morphology: Root <ul><li>Human hair grows in three developmental stages: anagen, catagen, and telogen phases </li></ul>
  • 21. Root: Anagen Phase <ul><li>Initial growth phase during which hair follicle is actively producing hair, phase may last 6 years, root is flame like in appearance </li></ul><ul><li>When pulled this root may contain a follicular tag (rich source of DNA) </li></ul>Anagen hair root Root w/ follicular tag
  • 22. Root: Catagen Phase <ul><li>A transition phase—hair grows at a decreasing rate for two to three weeks—elongated appearance as root bulb shrinks and is being pushed out of hair follicle </li></ul>Catagen hair root
  • 23. Root: Telogen phase <ul><li>Hair growth has ended—root takes on a club-like appearance, the hair will be pushed out of the follicle causing the hair to shed naturally </li></ul>Telogen hair root
  • 24.  
  • 25. Types of hair: curly vs. straight
  • 26. Hair in the anagen phase Electronmicrograph showing new hairs emerging from the hair follicles of the scalp
  • 27. Telogen phase showing the “clubed” appearance
  • 28. Appearance of the root of pulled human hair
  • 29. <ul><li>Razor cut tip of hair: Blunt cut tip of hair: </li></ul>
  • 30. Split hair tips
  • 31. Fragments and debris on hair
  • 32. Lice- nits (egg cases on hair shaft)
  • 33. Matching hair using a comparison microscope
  • 34. Important Forensic Questions <ul><li>Can the body area from which a hair originated be determined? </li></ul><ul><li>Can the racial origin of hair be determined? </li></ul><ul><li>Can the age and sex of an individual be determined from a hair sample? </li></ul><ul><li>Is it possible to determine if a hair was forcibly removed from the body? </li></ul><ul><li>Are efforts being made to individualize human hair? </li></ul><ul><li>Can DNA individualize a human hair? </li></ul><ul><li>Define nuclear and mitochondrial DNA—note similarities and differences </li></ul><ul><li>Find answers in text pgs 201 - 204 </li></ul>
  • 35. Fibers: Natural <ul><li>Derived entirely from animal or plant sources </li></ul><ul><li>Most prevalent plant fiber is cotton. </li></ul><ul><li>Its widespread use has made its evidential value almost meaningless </li></ul><ul><li>Cotton has a ribbon-like shape with twists at regular intervals </li></ul><ul><li>Animal sources include sheep (wool), goats (mohair, cashmere) and many other sources </li></ul>
  • 36. Man-Made Fibers <ul><li>Fibers derived from either natural or synthetic polymers </li></ul><ul><li>The fibers are made by forcing polymeric material through the holes of a spinneret </li></ul><ul><li>Rayon and then nylon were the first two man-made fibers (year 1911) </li></ul>
  • 37. Man-Made Fibers Con’t <ul><li>Regenerated Fibers </li></ul><ul><ul><li>Made from regenerated cellulose (wood or cotton pulp) </li></ul></ul><ul><ul><li>Include such fibers as rayon, acetate, and triacetate </li></ul></ul><ul><li>Synthetic Fibers </li></ul><ul><ul><li>Currently manufactured </li></ul></ul><ul><ul><li>Made from synthetic chemicals called polymers </li></ul></ul><ul><ul><li>Include such fibers as nylons, polyesters, and acrylics </li></ul></ul>
  • 38. Polymers <ul><li>Basic chemical substance of all synthetic fibers </li></ul><ul><li>Consist of long chains of repeating molecules. The repeating molecular units in the polymer are called monomers. </li></ul><ul><li>Often referred as macromolecules or “big” molecules </li></ul><ul><li>Countless varieties exist </li></ul>
  • 39. ID and Comparison of Man-Made Fibers <ul><li>Fabrics that can be fitted together at their torn edge are easy to match </li></ul><ul><li>Microscopic comparison of color and diameter </li></ul><ul><li>Comparison of lengthwise striations and pitting on the surface of a fiber </li></ul><ul><li>The shape of the fiber—ex. Wayne Williams case </li></ul><ul><li>Note: Combined factors of color, size, shape, microscopic appearance, chemical composition, and dye content make it very unlikely to find two different people wearing identical fabrics </li></ul>
  • 40. Tools and Techniques to Aid in Comparing Fibers <ul><li>Light infrared spectrophotometer—compares colors and chemical composition through spectral patterns </li></ul><ul><li>Chromatography—compares dye composition </li></ul><ul><li>Refraction—ID’s fiber by refractive index </li></ul><ul><li>Comparison microscope—reveals shape, coloring, pitting and striations </li></ul>
  • 41. Forensic Examination of Paint <ul><li>Paint evidence is frequently encountered in hit-and-run and burglary cases </li></ul><ul><li>Most examinations consist in comparing two or more paints to establish their origin </li></ul><ul><li>Often color, make and model of a vehicle can be determined </li></ul>
  • 42. Paint Characteristics <ul><li>Paint spread on a surface will dry into a hard film consisting of pigments and additives suspended in a binder </li></ul><ul><li>The binder provides the support medium for the pigments and additives. </li></ul><ul><li>Modern automotive finishing consists of at least four coatings: </li></ul><ul><li>Electrocoat Primer : first layer, electroplated to the car—provides corrosion resistance—color from black to grey </li></ul><ul><li>Primer Surface : second layer, smoothes out and hides any seams on the car—color pigments are used to minimize contrast between primer and topcoats </li></ul><ul><li>Basecoat: third layer, provides the basic color and appearance to the car </li></ul><ul><li>Clearcoat: final coat, provides great appearance (glossiness) and protection for the car </li></ul>
  • 43. Tools and Techniques to Aid in Paint Examination <ul><li>Questioned and known specimens are compared side by side under a stereomicroscope for color, surface texture, and color layer sequence </li></ul><ul><li>Note: Layer sequence is very important evidence: forensic scientists will try to match layers with respect to number and sequence of color </li></ul><ul><li>Note: Layer structure alone will not provide enough information to be individualized to a single source </li></ul><ul><li>Chemical analysis of the paint’s pigments and binder composition provides further points of comparison. </li></ul><ul><li>Typically, gas chromatography is used to determine the chemical make-up of the binder material. </li></ul><ul><li>Infrared spectrophotometry is also used to determine the binder composition of paint. </li></ul><ul><li>Elements of the paint pigments can be identified with a number of techniques, including spectroscopy, neutron activation analysis, and x-ray diffraction </li></ul><ul><li>Using these techniques the odds against crime-scene paint originating from another randomly chosen vehicle is approximately 33,000 to one. </li></ul>

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