Fiber Analysis

1. Fiber Analysis Chapter 7

2. Objectives • Identify and describe common weave patterns of textile samples • Compare and contrast various types of fibers through physical and chemical analysis • Describe principle characteristics of common fibers used in their identification • Apply forensic science techniques to analyze fibers

3. Vocabulary • Amorphous: without a defined shape; fibers composed of a loose arrangement of polymers that are soft, elastic, and absorbing (for example, cotton) • Crystalline: regularly shaped; fibers composed of polymers packed side by side, which make it stiff and strong (for example, flax) • Direct transfer: the passing of evidence such as a fiber, from victim to suspect or vice versa

4. Vocabulary • Fiber: the smallest possible indivisible unit of a textile, it must be at least 100 times longer than wide • Mineral fiber: a collection of mineral crystals formed into a recognizable pattern • Monomer: a small molecule that may bond to other monomers to become a polymer • Natural fiber: a fiber produced naturally and harvested from animal, plant, or mineral sources

5. Vocabulary • Polymer: a substance composed of long chains of repeating units • Synthetic fiber: a fiber made from a man-made substance such as plastic • Secondary transfer: the transfer of evidence such as a fiber from a source (for example, a carpet) to a person (suspect), and then to another person (victim) • Textile: a flexible, flat material made by interlacing yarns (or “threads”)

6. Vocabulary • Yarn: fibers that have been spun together

7. Introduction • Fibers can link crime and suspect • We wear clothes, we shed fibers • Walk on carpet, sit on couch, pull on sweater • Fibers fall off or picked up • Fibers are not specific, but can be useful source of evidence

8. Introduction • Trace evidence • Come from carpets, clothing, linens, furniture, insulation, rope • Direct transfer (suspectvictim or vic versa) • Secondary transfer (sourcesuspectvictim)

9. Checkpoint • IF a carpet fiber were transferred from the clothing of a victim to his attacker…direct or secondary? • Secondary • Carpet went to the victim then to the attacker

10. How Forensic Scientists Use Fibers • Early collection of fibers in an investigation is critical • In 24 hours, 95% of fibers on victim or crime scene may have been lost or fallen off • ONLY fibers that are not expected to find are investigated… • If pink fibers are found on victims clothes and suspects house has wall to wall pink carpet- the forensic scientist would NOT examine these • Value of fiber depends on uniqueness

11. Questions for Fibers • Type of Fiber • Composition of fiber– how common or rare? What suspect of victims or part of crime scene had this type of fiber? • Fiber Color • To fibers on suspects clothing match the victims house? Is the type of dye the same? • Number of fibers found • More fibers suggest violence or longer period of contact • Where the fiber was found • Just in the house or right next to the victims body? How close can you place the suspect to the scene of the crime?

12. Questions for Fibers • Textile the fiber originated from • Are they from a carpet? Or car upholstery? • Multiple fiber transfers • Is there one type of fiber? Or many from clothing, carpet, bedding, automobile…more types suggests longer contact or violence • Type of crime committed • Was it a kidnapping? A break and enter? A violent crime? Each type of crime has a typical pattern of fiber transfer • Time between crime and discovery of fiber • The value of fiber found is reduced with passage of time bc fibers will fall off or fibers not related can be picked up

13. Sampling and Testing • Special vacuums, sticky tape, and forceps • WHERE the evidence is found is noted • Inaccurate and incomplete recording of evidence… inadmissible in court

14. Sampling and Testing • 1st- FS collects small amounts, maybe one fiber from CS • Study type of fiber and characteristics of it • Shape, color • 2nd- FS match to suspect source • Car or home • Only one small tiny fiber may be recovered • Cannot do tests that damage or alter fiber

15. Fiber and Textile Evidence • Textiles: clothing, carpets, and upholstery • Textiles are constructed by weaving, or intertwining together yarns. • Yarns are made up of fibers that have been “spun” together • NATURAL fibers • SYNTHETIC fibers

16. You Think • What are the natural fibers you think of? • Animal fibers • Plant fibers • Seed fibers • Fruit fibers • Stem fibers • Leaf fibers • Mineral fibers • What are the synthetic fibers you think of? • Regenerated fibers • Synthetic polymer fibers • Acrylic • Olefins • Polyester • nylon

17. Activity- Fiber Evidence Analysis • Analysis focuses on shape, size, composition, dye content, visual appearance • Color and Fiber diameter is first to be determined using a compound microscope • See striations that are not visible to the eye • Variation in color bands • Bundle of small threads, not a monofilament

18. Natural Fibers • Animals, plants, and minerals that are mined from the ground • ANIMAL: • Hair, fur, and webbing • Made of proteins • In clothing, carpets, curtains, and bedding • Fur: fibers… though not a textile. Animal is trapped and skin is removed and treated (flexible skin that retains fur) • Used for coats and gloves

19. Natural Fibers • Hair- brushed out of animal coat • Ex: wool from sheep • Cashmere & mohair from goats • Angora from rabbits • Hair from Camel, alpaca, and llamas • For bedding, clothing, heavy coats, carpets, bags, and furniture upholstery • Made into textiles- spun loosely- textiles shed fibers easily

20. Natural Fibers • Silk- caterpillars are held captive, and each cocoon is unwound by hand • Shimmering appearance of silk is due to triangular structure of fiber, which scatters light like a prism • Used in clothing and bedding • Don’t shed as easily as hair fibers

21. Plant Fibers- Natural • All contain cellulose • Become brittle over time • Seed fibers (ex cotton) • Fruit fibers (coir fiber on the outside of coconuts; used for door mats) • Stem fibers (from thick regions of stems, grows in bundles, ex: hemp, jute (too rough for clothing, used for rope, handbags, twine), flax (most common- linin)) • Leaf fibers (manilla- from banana relative abaca) • Mineral fibers (NOT protein or cellulose) fiberglass (short weak brittle fibers, insulates buildings, causes irritation); asbestos (crystalline structure, very durable, pipe coverings, break linings, ceiling tiles, floor tiles, fire resistant work clothes, shingles, siding, insulation- KNOWN Carcinogen!!!- inhalation causes cuts in throat.. leads to cancer)

22. Synthetic (Man-made) Fibers

23. DID YOU KNOW?? • Silk cocoons are 2.5cm long and are made from ONE fiber that may measure 1 to 2 km long! It takes 3,000 of these cocoons to make 1 square meter of fabric

24. Sampling and Testing • FS then tries to match that fiber to the suspect source like car or home • Must perform tests that do not damage that ONE fiber • Polarizing light microscopy • Infrared spectroscopy

25. Polarized light microscopy • Uses microscope that has special filter in it that allows the scientist to look at fiber using specific wave lenghts • Type of fiber can be determined (linen  ) • Natural fibers (wool/cotton) require only an ordinary microscope to view characteristic shape and markings • Birefringment: light property of synthetic fibers, refract light at different angles; can identify type of fiber

26. Compound microscope • Natural fiber (cotton, wool) • See characteristic shapes and markings • Cotton looks like twisted ribbon • Wool is cylindrical and covered with scales • Linen looks like bamboo with joints • Silk looks like smooth glass rod with elliptical shapes sometimes (caused by marking with gum that is not removed)

27. Infrared Spectroscopy • Infrared spectroscopy emits a beam that bounces off the material and returns to the instrument • How the beam of light changes reveals the chemical structure of the fiber • Fibers that LOOK alike will have a different chemical structure

28. Burn Method • If many fibers are found, some of the fibers will be subject to destructive testing • Burn analysis • Dissolving in various liquids • Silk stops burning immediately when flame is removed (silk)

29. QUIZ # 2 • T/F: A polymers are long chain molecules composed of smaller units called monomers • T/F: Sugar molecules form proteins • T/F: Amino acids form diamonds • T/F: ethylene forms polyethylene • T/F: catalysts cause a chemical reaction • Condensation is the loss of __________ to combine two molecules • Molecules with branching structures are very _____ (weak/strong) • Give ONE example of a natural polymer. _______________

30. QUIZ # 2 • T/F: A polymers are long chain molecules composed of smaller units called monomers • T/F: Sugar molecules form proteins • T/F: Amino acids form diamonds • T/F: ethylene forms polyethylene • T/F: catalysts cause a chemical reaction • Condensation is the loss of WATER to combine two molecules • Molecules with branching structures are very _____ (weak/strong) • Give ONE example of a natural polymer: • Proteins • Polysaccharides • Nucleic acids • Asbestos • Graphite