Fibers and Textiles

Chapter 4

Objectives

0 Identify and describe common patterns of textile samples

0Compare and contrast various types of fibers through physical and chemical analysis

0Describe principal characteristics of common fibers used in their identification

0Apply forensic science techniques to analyze fibers

Introduction

0Fibers are used in Forensic Science to create a link between crime and suspect.

0Fibers are a form of Trace Evidence. 0Direct transfer is when a fiber is transferred from

victim to suspect or vice versa. 0Secondary transfer is a fiber that was picked up and

then transferred to a suspect, or from original source to the suspect then to the victim.

How FS use Fibers

0Evidence of any kind should be evaluated, especially fibers because there are so many of them in each environment.

0Their value depends on their uniqueness0 White cotton fiber vs. angora fiber

Uses of Fibers

0Type of Fibers

0Fiber Color

0Number of Fibers Found

0Where Fiber was Found

0Textile the fiber originated from

Uses of Fibers0 Multiple Fiber Transfers

0 Type of crime committed

0 Time between crime and discovery of fiber

Sampling and Testing0Fibers are gathered with special vacuums, sticky tape,

and forceps. 0First task is to identify the fibers type and its

characteristics0 Shape and color

0Polarized lightmicroscopy

0 Infrared Spectroscopy0Large amounts ofFibers allow testing

Textiles

0The most common form of fiber transfer found at a crime scene: shredding of a textile

0Clothing, carpets, upholstery

0Constructed by weaving, or intertwining together

0Yarns – fibers that have been “spun” together

Fiber Classification

0Natural Fibers0 From animals, plants, and

minerals that are minded from the ground

0Synthetic Fibers (man-made)0 Regenerated fibers and

polymers. 0 Produced by joining many

monomers together to form polymers

Natural Fibers0Animal Fibers

0 Hair, fur, and webbing0 All are made of proteins

0Fur fibers 0 Good donor of fibers, but not a textile0 Used primarily for coats and gloves

Natural Fibers0Animal Fibers Cont’d0 Hair fibers

0 Most popular animal fibers0 Brushed out, shed, collected and clipped

naturally from animals 0 Most common animal hair used in

textile is Wool from sheep0 Webbed Fibers

0 Silk, collected from cocoons of the caterpillar Bombyx mori

0 Because silk fiber are very long, they tend not to shed as easily as hair fibers

Natural Fibers0Plant Fibers

0 Specialized plant cells0 Grouped by which part of the plant they

come from0 Seeds, fruits, stems, and leaves

0 Fibers differ greatly in physical characteristics

0 Amorphous – loose arrangement of fibers that are soft, elastic, and absorbent.

0 All plant fibers contain Cellulose0 Polymer the that is made up of simple

glucose units 0 Cotton is the most common plant fiber

Natural Fibers (plants)

0 Seed fibers0 Cotton is found in the seedpod of

the cotton plant.0 Fruit fibers

0 Coir is a course fiber obtained fro the covering surrounding coconuts.

0 Individual cells of coir fibers are narrow, with thick walls made of cellulose; woven together are stronger than flax or cotton.

0 Relatively waterproof (doormats and baskets)

Natural Fibers (plants)

0 Stem fibers0 Hemp, jute, and flax are all produced

from the thick region of plant stems. 0 Grow in bundles, can extend the entire

length of a plant0 Flax is most common stem fiber and is

most commonly found in the textile linen.

0 Leaf fibers0 The fiber bundles are taken from the

surface of the leaves, and when bound together can reach long lengths.

0 Manila from abaca (relative of banana tree)

0 Sisal desert plant used to make ropes, nettings and twines

Natural Fibers (plants)

0Mineral fibers0 Neither protein or cellulose. 0 Fiberglass fiber- form of glass

where its fibers are very short, very weak, and brittle.

0 Asbestos – mineral naturally occurring in rocks with a crystalline structure composed of long, thin fibers. Very durable.

Synthetic Fibers

0Regenerated fibers0 Derived from cellulose and are made mostly plant in

origin. 0 Rayon is most common. 0 Cellulose chemically combined with acetate or 3 acetate

units, form Celanese and polyamide nylon (Capron)

Synthetic Fibers

0Synthetic Polymer Fibers0 Originate with petroleum

products and are non-cellulose based.

0 100% man-made0 No definite shape or size and

can be easily dyed.

Synthetic Polymer Fibers0 Polyester

0 Represents large group of fibers with a common chemical makeup

0 Polar fleece, wrinkle-resistant pants, and added to many natural fibers to provide additional strength.

0 Nylon0 Similar to polyester, except is

easily broken down by light and concentrated acid.

0 Acrylic 0 Often found in artificial wool or

imitation fur; light fluffy feel0 Olefins

0 High-performance clothing (thermals, socks, carpets)

0 Quick drying and resistant to wear