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  1. Fibers Criminalistics

  2. 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.

  3. Fibers • Comprise our fabrics and garments. • Important evidence in incidences that involve personal contact: Homicides, assaults, & sexual offenses Can also be transferred in hit-and-run cases.

  4. Problems with Fiber Analysis • Mass production of garments and fabrics has limited finding origin points. • It is very unusual to identify fiber evidence with a high degree of certainty. • i.e. pinpoint the type of garment and brand. • Eg. Ralph Lauren polo shirt!

  5. Natural Fibers • Derived in whole from animal or plant sources. • Animal sources: sheep, goats, camels, llamas, alpacas, mink, rabbit, beaver, and muskrat • Plant sources: primary source Cotton Wool Fibers Cotton Fibers

  6. 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.

  7. Natural Fibers Natural fibers will look rough on the edges, with a rather rough shape to the cross section as well. The animal fiber most frequently used in the production of textile materials is wool, and the most common wool fibers originate from sheep.

  8. Loose Weave Cotton Shirt - 100x (Photo by Mr. Lazaroff) Cotton Jeans - 100x  (Photo by Mr. Lazaroff)

  9. Merino Wool, with tiny overlapping scales in the cuticle (look at the edges)From

  10. Synthetic Fibers More than half of all fibers used in the production of textile materials are synthetic or man-made. Nylon, rayon, and polyester are all examples of synthetic fibers. Images:

  11. Fibers under a microscope Synthetic Fibers Cross section of synthetic fibers will have a greater variation:  Round, Oval, Bilobal (two lobes), and Trilobal (three lobes) Cross-section of a man-made fiber Images:

  12. Identification and Comparison of Man-Made Fibers • Microscopic comparison using a comparison microscope: • Cuticle • Color and Diameter • Striations and Pitting • Shape of Fiber in Cross-Section

  13. Identification and Comparison of Man-Made Fibers • Chromatography • Separate shades of color on a chromatograph

  14. Identification and Comparison of Man-Made Fibers • Test chemical composition. • Fibers are separated into classes.

  15. Identification and Comparison of Man-Made Fibers • Light Analysis • Light passing through a fiber will be polarized and have a specific index of refraction. • Refraction indexes can be compared.

  16. Problems with Fiber ID • Fiber strands cannot be linked with any certainty to any single garment or origin: • Due to mass production of clothing, carpets, and other fiber sources.

  17. Packaging of Fiber Evidence • Articles of clothing must be packaged separately in paper bags. • Carpets, rugs, and bedding must be folded carefully to preserve fiber evidence. • Car seats must be covered in plastic sheets. • Knife blades should be coveredto protect fibers that may be stuck to them.

  18. Packaging of Fiber Evidence • If the possibility exists that the evidence would be lost in moving it from the crime scene: • Fibers need to be removed from evidence before it goes to the lab: • Clean forceps must be used and the evidence double enveloped.

  19. Fiber Evidence There are several reasons why fibers are a useful form of evidence: 1.  They are easily transferred. 2.  They are capable of multiple transfers (thus illustrating a series of events).

  20. Fiber Evidence 3.   Fibers vary depending on their specific end use (i.e., carpet fibers, which need to be more durable, are different from clothing fibers). 4.   Fibers exist in a huge variety!

  21. Fiber Evidence • 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.

  22. (1) NOTE the SMOOTH EDGES to all the Synthetic Fibers!(2) NOTE the LUSTER (Shine) to all the Synthetic Fibers! Synthetic - 100x  (Photo by Mr. Lazaroff)





  27. It’s time to examine some hairs and fibers!

  28. Fiber Identification Lab Directions: Your team will need to use a microscope to document all the fibers in your set. Write the name of the fiber on the line and then draw what you see under medium or high power. Be sure to indicate the power of magnification! Add a description that highlights the unique characteristics of each fiber sample. Pay attention to details to help you identify samples during the Fiber Challenge activity.

  29. Can you identify the animal hairs shown? A B C D G E F H I • Think About It … • In which samples are we viewing the cuticle? How do they compare? • (2) In which samples are we viewing the medulla? How do they compare? • (3) What characteristics can be used to identify hair samples?

  30. Can you identify the types of fibers shown? A B C D E F • Think About It … • Which samples are natural fibers? • (2) Which samples are synthetic fibers? • (3) What characteristics can be used to identify fiber samples?

  31. Answer Keys

  32. Types of Animal Hairs - Key Cat Horse Pig Human A B C D G E F H I Deer Dog Rabbit Rat Human

  33. Types of Fibers - Key A B C Acrylic Yarn Cotton Yarn Nylon Rope D E F Polyester Yarn Rayon Rope Wool Yarn