1. Chapter 4: A Study of Fibers and Textiles ● Atlanta Child Murders Forensic Science: Fundamentals & Investigations, Chapter 4 http://www.youtube.com/watch?v=-G74DFA9390

2. Forensic Science: Fundamentals & Investigations, Chapter 4 Chapter 4 A Study of Fibers and Textiles By the end of this chapter you will be able to: ● Identify and describe common weave patterns of textile samples ● Compare and contrast various types of fibers through physical and chemical analysis ● Describe principle characteristics used to identify common fibers ● Apply forensic science techniques to analyze fibers All Rights Reserved South-Western / Cengage Learning © 2012, 2009

3. Vocabulary ● Amorphous ● Crystalline ● Direct transfer ● Fiber ● Mineral fiber ● Monomer ● Natural fiber ● Polymer ● Synthetic fiber ● Secondary fiber ● Textile ● yarn Forensic Science: Fundamentals & Investigations, Chapter 1

4. Forensic Science: Fundamentals & Investigations, Chapter 4 Introduction ● Fibers are used in forensic science to create a link between crime and suspect ● Through every day normal activities we o shed fibers o picked up fibers ● Fibers are classified as trace evidence

5. Forensic Science: Fundamentals & Investigations, Chapter 4 How Do Forensic Scientists Use Fibers? Fiber evaluation can show ● Type of fiber ● Color ● Possibility of violence ● Location of suspects ● Point of origin

6. Forensic Science: Fundamentals & Investigations, Chapter 4 How Do Forensic Scientists Obtain Fibers? ● Special vacuums ● Sticky tape ● Lint Rollers ● Forceps

7. Forensic Science: Fundamentals & Investigations, Chapter 4 Methods of Analyzing Fibers ● Without Damaging Fibers ● Microscopes reveal characteristic shapes and markings (Infrared microscopy) ● Infrared spectroscopy reveals chemical structures to differentiate similar fibers ● Destructive Testing Methods ● Burning fibers ● Dissolving fibers in various liquids

8. Forensic Science: Fundamentals & Investigations, Chapter 4 Methods of Analyzing Fibers: Stereoscopic Microscope The most commonly used microscope in crime labs Stereo Microscope Compound Microscope

9. Forensic Science: Fundamentals & Investigations, Chapter 4 Methods of Analyzing Fibers: Stereoscopic Microscope ● Two separate monocular microscopes each with its own set of lenses ● Produce a three-dimensional image with a right-side-up, frontward orientation ● Offers a large working distance for bulky items ● Relatively low magnification (10x-125x) ● Can be lighted from below or vertically from above ● This microscope is actually two separate monocular microscopes except for the lowest objective lens, which is common to both microscopes

10. Forensic Science: Fundamentals & Investigations, Chapter 4 Methods of Analyzing Fibers: Polarizing Microscope ● Polarizing microscopes ● Include two polarizing filters, a polarizer lens (fixed below the specimen), and an analyzer lens (fixed above the specimen) ● The stage with the sample is rotated to determine how the polarized light interacts with the sample

11. Forensic Science: Fundamentals & Investigations, Chapter 4 Methods of Analyzing Fibers: Polarizing Microscope This can provide information about the shape, color, and size of minerals and it is used to identify hair, human-made fibers and paint. Hair Sample: Polarized Light Hair Sample: Natural Light

12. Forensic Science: Fundamentals & Investigations, Chapter 4 Sampling and Testing: An Example

13. Forensic Science: Fundamentals & Investigations, Chapter 4 HOW ARE FIBERS CLASSIFIED? FIBERS ARE CLASSIFIED AS EITHER ● Natural: Animal, Plants, Minerals ● Synthetic: Man Made

14. Forensic Science: Fundamentals & Investigations, Chapter 4 HOW CAN WE TELL THE DIFFERENCE BETWEEN SYTHETIC AND NATURAL FIBERS? ● Step 1: Natural vs synthetic, use a comparison microscope ● Examine the color, diameter, cross-section shape, pitting or striations, etc. ● Synthetic fibers have smooth surfaces, uniform size & shape

15. Forensic Science: Fundamentals & Investigations, Chapter 4 HOW CAN WE TELL THE DIFFERENCE BETWEEN SYTHETIC AND NATURAL FIBERS? ● Step 2: chemical composition of synthetics ● Use IR spectroscopy, refractive index or polarized light to identify types of synthetic fiber ● Dye can be extracted and the colors separated by thin layer chromatography (TLC)

16. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Natural Fibers Animal fibers (made of proteins) : ● Wool and cashmere from sheep ● Mohair from goats ● Angora from rabbits ● Hair from alpacas, llamas, and camels ● Silk from caterpillar cocoons (longer fiber does not shed easily) woven wool textile

17. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Natural Fibers Plant fibers (made of the polymer cellulose) : ● Absorb water ● Insoluble in water ● Very resistant to damage from harsh chemicals ● Dissolvable only by strong acids ● Becomes brittle over time

18. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Natural Fibers Plant fibers: ● Cotton—most common textile plant fiber (picture) ● Coir from coconuts is durable ● Hemp, jute, and flax from stems grow in bundles ● Manila and sisal from leaves deteriorate more quickly

19. Fiber Classification —Natural Fibers Seed fibers – Cotton is found in the seedpod of the cotton plant. Because of the ease with which cotton can be woven and dyed, it has been used extensively for clothing and household textiles. Fruit fibers – Coir is a coarse fiber obtained from the covering surrounding coconuts. When woven together, they are stronger than flax or cotton. Coir fiber is relatively waterproof which makes it ideal for such things as doormats and baskets. Stem fibers – Hemp, jute, and flax are all produced from the thick region of plant stems. They do not grow as single, unconnected fibers like cotton, but in bundles. These bundles may be six feet in length and extend the entire length of a plant. 19

20. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Natural Fibers Mineral Fibers: ● Fiberglass—a fibrous form of glass ● Asbestos—a crystalline structure

21. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Synthetic Fibers ● 50% of fabrics are artificially produced ● Examples: o Rayon o Acetate o Nylon o Acrylic o Polyester

22. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Synthetic Cellulose Fibers Regenerated Fibers (derived from cellulose) : ● Rayon o Most common in this group o Imitates natural fibers, but stronger ● Celenese ® o Cellulose chemically combined with acetate o Found in many carpets ● Polyamide nylon o Cellulose combined with three acetate units o Breathable and lightweight o Used in performance clothing

23. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Synthetic Polymer Fibers Synthetic Polymer Fibers ● Petroleum base ● Very different from other fibers ● Monomers join to form polymers ● Fibers are spun together into yarns ● No internal structures ● Uniform diameters

24. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Synthetic Polymer Fibers ● Polyester o “Polar fleece” o Wrinkle-resistant o Not easily broken down by light or concentrated acid o Added to natural fibers for strength ● Nylon o Easily broken down by light and concentrated acid o Otherwise similar to polyester spandex nylon

25. Forensic Science: Fundamentals & Investigations, Chapter 4 Fiber Classification —Synthetic Polymer Fibers ● Acrylic o Inexpensive o Tends to “ball” easily o Substitute for artificial wool or fur ● Olefins o High performance o Quick drying o Resistant to wear

26. Forensic Science: Fundamentals & Investigations, Chapter 4 Comparison of Natural and Synthetic Fibers Visual Diagnostics of Some Common Textile Fibers under Magnification

27. Forensic Science: Fundamentals & Investigations, Chapter 4 Yarns, fabrics, and textiles ● Yarns—fibers (of any length, thick or thin, loose or tight) twisted or spun together ● Blending fibers meets different needs (e.g., resistance to wrinkling) ● Fibers are woven into fabrics or textiles o Threads are arranged side by side (the warp) o More threads (the weft) are woven back and forth crosswise through the warp

28. Forensic Science: Fundamentals & Investigations, Chapter 4 Weave Patterns

29. Forensic Science: Fundamentals & Investigations, Chapter 4............. Summary.... ● Fibers are a form of class evidence. ● Fibers are a form of trace evidence. ● Fibers are spun into yarns having specific characteristics. ● Yarns are woven, with different patterns, into clothing or textiles. ● Fiber evidence is gathered using different techniques.

30. Forensic Science: Fundamentals & Investigations, Chapter 4................. Summary ● Fibers are analyzed using burn tests, tests for solubility in different solutions, polarized light microscopy, or infrared spectroscopy. ● Fibers are classified as natural or synthetic. ● Natural fiber sources include: o Animal hair o Plant seeds, fruit, stems, or leaves o Minerals.