Someone stole a CD and a portable CD player from the mall music store. Shady Shrew claims he saw the stork unwrap those items and immediately start listening to music. Slylock Fox strongly suspects Shady's account is false. Why? Source:

Fiber Evidence

A fiber is the smallest unit of a textile material that has a length many times greater than its diameter. 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. The discovery of cross transfers increases the likelihood that these two individuals had physical contact.

Forensic Science: Fundamentals & Investigations, Chapter 4 4 Sampling and Testing How are fibers collected? – Special Vacuums – Sticky Tape – Forceps (tweezers) – Black Lights – Magnifying Glasses

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. Natural Fibers

Natural Fibers: Animal Fibers Sheep (wool) most common; the end use is often determined by coarseness fine wool fibers are used for clothing, while coarse wool fibers are used in carpeting Goat (mohair, cashmere) Camel (wool) Llama Alpaca (wool) Fur fibers from mink, rabbit, beaver, etc. Silk (fiber from the cocoon of the silkworm) 6 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Natural Fibers: Plant Fibers Cotton (ribbon-like shape with irregular twists; most common) Flax (Linen) Ramie Sisal (often used in linen rugs) Jute (used in ropes) Hemp (the common name for cannabis for industrial or non- drug use; typically used for rope or sack) Kapok (fiber from kapok tree seed pods; used in pillows and mattress stuffing) Coir (coconut husks; used in carpet, rugs) 7 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Forensic Science: Fundamentals & Investigations, Chapter 4 8 Fiber Classification —Natural Fibers Plant fibers (made of the polymer cellulose): can absorb water. are insoluble in water. are very resistant to damage from harsh chemicals. can only be dissolved by strong acids. can be common at crime scenes because they become brittle over time.

Images: 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. Cross-section of a man-made fiber Synthetic Fibers Fibers under a microscope

Forensic Science: Fundamentals & Investigations, Chapter 4 10 Fiber Classification —Synthetic (artificially produced) Fibers Until the nineteenth century only plant and animal fibers were used to make clothes and textiles. Half the products produced today are artificially produced. Artificially produced fibers include rayon, acetate, nylon, acrylics, and polyesters.

Federal Trade Commission Rules and Regulations Under the Textile Products Identification Act, 1954 Generic names for manufactured fibers Acetate Acrylic Anidex Aramid Glass Lyocel Nylon Metallic Modacrylic Novoloid Olefin Polyester Rayon Saran Spandex Vinal Vinyon

Synthetic Fibers More than half of all fibers used in the production of textile materials are manmade. Polyester (most common; wrinkle resistant; often spun with cotton) Nylon (very common; elastic and strong; lustrous and silk-like when stretched) Acrylics (wool-like, soft and warm; quick drying and resistant to moths) Rayon (cellulose-derived, regenerated, thin fiber) Acetates (cellulosed-based, wrinkle-resistant fiber) 12 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Man-Made Fibers The cross section of a man- made fiber can be manufacturer-specific Some cross sections are more common than others, and some shapes may only be produced for a short period of time. Unusual cross sections encountered through examination can add increased significance to a fiber association. Cross-sectional views of nylon carpet fibers as seen with a scanning electron microscope (SEM)

Forensic Science: Fundamentals & Investigations, Chapter 4 14 Comparison of Natural and Synthetic Fibers Visual Diagnostics of Some Common Textile Fibers under Magnification

Forensic Fiber Analysis The world produced approximately 80 billion pounds of fabric in 1995, about half of which was cotton The other approximately 44 billion pounds of fiber were manufactured or synthetic. Table 1. U.S. Annual Production for Manufactured Fibers: 1995 (millions of pounds) FiberProduct Polyester3,887 Nylon270 Olefin521 Rayon/Acetate/Triace tate 498 Acrylic/Modacrylic432 (Table 1 [6]). All these fibers were used in a variety of applications including but not limited to clothing, household textiles, carpeting, and industrial textiles. Why would this information be valuable to a forensic scientist?

Lengthwise threads (the warp) are woven by crosswise threads (the weft) in a pattern. Common Weave Patterns Plain (firm, tends to wrinkle) Basket (not very durable, shrinks when washed) Satin (not durable, shiny surface) Twill (very strong, dense and compact, soft) Leno (open weave, easily distorted) Weaving Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Forensic Science: Fundamentals & Investigations, Chapter 4 17

Forensic Science: Fundamentals & Investigations, Chapter 4 18 Yarns, Fabrics, and Textiles Weave Patterns

Fiber Comparisons Microscopic Comparisons Color Diameter Surface markings Cross-sectional shape 19 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Polarized Light Microscopy – determines birefringence (difference between two refractive indices) using polarized light Fiber Comparisons (continued) 20 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fourier Transform Infrared Spectroscopy (FTIR) – analysis of a fiber’s chemical composition based on its ability to absorb light at different wavelengths Fiber Comparisons (continued) 21 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

UV-Visible Microspectrophotometry – distinguishes slight/subtle color differences based on absorption of light at different wavelengths Fiber Comparisons (continued) 22 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Forensic Science: Fundamentals & Investigations, Chapter 4 Introduction and How Forensic Scientists Use Fibers In an investigation, collection of fibers within 24 hours is critical. – Why? Fiber evaluation can show such things as the type of fiber, its color, the possibility of violence, location of suspects, and point of origin.