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Fibers Chapter 6

Fibers Chapter 6. Fibers. Fibers are made up of many filaments twisted or bonded together to form a thread. Along with hair, fibers are the most common type of trace evidence left at a crime scene.

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Fibers Chapter 6

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  1. Fibers Chapter 6

  2. Fibers • Fibers are made up of many filaments twisted or bonded together to form a thread. • Along with hair, fibers are the most common type of trace evidence left at a crime scene. • They are considered class evidence, but the evidence can be probative by creating connections and associations.

  3. Sources and types of fibers • Sources of fibers include animals, plants, or synthetic. • Fibers are used to make clothing, carpeting, rope, string, or nets. • Fabric is made from fibers and each fabric has its own unique characteristics. • Fabrics are made by weaving, knitting, crocheting, knotting, or felting.

  4. Weaves • In a weave the lengthwise yarn is called the warp, and the crosswise yarn is called the weft. • The warp is usually stronger, smoother, and more even than the weft. • Often the warp and the weft are made of different materials and are referred to as a blend. • Natural fibers include cotton, wool, hemp, and silk. • Artificial fibers include nylon, polyester, and acrylics.

  5. Chemical Structure of Fibers • Fibers are made of polymers. Wool is composed of polypeptide chains of amino acids that combine to form keratin. • Silk is a protein that is produced by the larvae of a moth. • Cotton is a plant fiber made of cellulose.

  6. These 2 functional groups make up what type of organic molecule?

  7. Synthetic Fibers • Common synthetic fibers include – polyesters such as dacron, nylon, and acrylic. See figure 2. • Polyesters are used in the production of:

  8. Fiber Analysis • Forensic evidence of fibers is based on their physical and chemical characteristics. • Types of analysis include; -Microscope investigation -Burn test -Chemical test -Density test -Refractive Index Test -Fluorescent Test -Dye Analysis -Chromatography

  9. Fiber Transfer • Fibers can be used as trace evidence. • Factors that affect transfer include – how long fibers remain on victim, fibers that can be transferred and then later lost…. • Make a list of other factors that can influence the transfer of a fiber.

  10. Fiber transfer in OJ Simpson Trial • Fibers from blue knit ski cap allegedly worn by Simpson the night of the murder found on his wife Nicole and Ronald Goldman. • Cotton fibers from Goldman’s shirt found in Simpson’s bedroom. • Fibers found on ski cap found at the crime scene and on the bloody glove found behind Simpson’s house were similar to the carpet fibers from Simpson’s Ford Bronco.

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