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Fiber Analysis

Fiber Analysis. Miss Stanley Middle School Science Club Forensic Division. Textile Fiber. A textile fiber is the basic unit or building block of a fabric. Fibers are produced naturally by plants and animals and synthetically by man. 3 Basic Fiber Categories. Natural

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Fiber Analysis

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  1. Fiber Analysis Miss Stanley Middle School Science Club Forensic Division

  2. Textile Fiber A textile fiber is the basic unit or building block of a fabric. Fibers are produced naturally by plants and animals and synthetically by man.

  3. 3 Basic Fiber Categories • Natural • Manufactured, or regenerated • Synthetic

  4. Natural Fibers Come from various animals, plants, and minerals. Examiners can often easily identify and compare these fibers by microscopic inspection alone. Animal hair that is woven into fabric or used to manufacture clothing and other household items is considered natural fiber.

  5. Natural Fiber - Cotton By far, the most commonly used natural fiber is cotton. When examined under a microscope, it has an easily recognizable twisted-ribbon pattern.

  6. Natural Fiber - Wool The most common animal fiber used in textile production is wool originating from sheep.

  7. Natural Fibers Other examples are mohair, cashmere, and silk. Plant fibers include cotton, hemp, flax, and jute.

  8. Manufactured or Regenerated Fibers Are fabrics like rayon, acetate, and triacetate. To make them, raw cotton or wood pulp is dissolved, and cellulose is extracted. The cellulose is then regenerated into fibers.

  9. Synthetic Fibers Come from polymers, which are substances made up of a series of monomers (single molecules) strung together to make larger molecules that can be thousands of monomers long. Nylon and polyester are synthetic fibers.

  10. Textile Definitions • Fiber is smallest unit of a fabric. • Fibers are twisted into yarns. • Yarns are knit or woven into fabrics. • Known or Standard fibers make up fabric of a donor or source garment. • Question or Transferred fibers are found on or recovered from (the debris from) a receptor garment.

  11. Fiber Evidence A fiber is the smallest unit of a textile material that has a length many times greater than its diameter. A fiber can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric. The type and length of fiber used, the type of spinning method, and the type of fabric construction all affect the transfer of fibers and the significance of fiber associations. This becomes very important when there is a possibility of fiber transfer between a suspect and a victim during the commission of a crime.

  12. Fiber Evidence Matching unique fibers on the clothing of a victim to fibers on a suspect’s clothing can be very helpful to an investigation, whereas the matching of common fibers such as white cotton or blue denim fibers would be less helpful. The discovery of crosstransfers and multiple fiber transfers between the suspect's clothing and the victim's clothing dramatically increases the likelihood that these two individuals had physical contact.

  13. Natural Fibers Many different natural fibers that come from plants and animals are used in the production of fabric. Cotton fibers are the plant fibers most commonly used in textile materials The animal fiber most frequently used in the production of textile materials is wool, and the most common wool fibers originate from sheep.

  14. Textiles Fibers as Evidence Crimes Against Persons: • Homicide, Assaults, Sex Crimes - used to indicate contact by transfer of fibers between V and S clothing, transfer of fibers between V/S and scene.

  15. Textiles Fibers as Evidence Crimes Against Persons: • Indication of Force in Crimes Against Persons - rips and tears. • Sabotage - cut or tied parachute lines.

  16. Textile Fibers as Evidence Crimes Against Property. • Burglary, Larceny, - torn fabric or loose fibers at point of entry, fabric marks from gloves, fibers from the scene transferred to suspect.

  17. Factors Influencing Transfer and Persistence • Studies show within 2 hours of transfer, 80% of fibers are gone. • Fiber type. • Weave or knit type. • Damage to the garment or fabric. • Amount or force of contact. • Garments vs. automobiles.

  18. Laboratory Examinations • Color - Dyes • Size - Diameter • Cross Sectional Shape • Transparent or Opaque • Chemical Composition

  19. Fiber Reports / Conclusions • How common is the fiber? • How many were found? • Is there a combination of fibers? (Consistent with one garment or one set of clothing?

  20. Laboratory Tests We’ll Do • Burning Characteristics • Solubility • Staining • Microscopic Appearance

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