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