Page 14 - Strands of Evidence Hair And Fiber

transferred. For example, a person merely sitting are actually generated from natural materials, such
on a rug will not pick up as much evidence as one as cotton, while others are completely synthetic.
rolling around on the rug. Examples of man-made fibers are polyester, nylon,
acrylic, rayon, and acetates — listed from most to
The overall condition of a garment and whether it is least common. Again, the rarer the fiber, the more
made of natural or synthetic fibers contributes to significant a match association becomes.
the ease at which fibers are deposited at a scene.
Both newer fabrics and older fabrics may increase In processing a fiber, cross-sectional analysis is
the likelihood of shedding fibers, as new fabrics have often required to make a match. Cross-sectional
an abundance of loosely adhering fibers and older shapes can identify a fiber type that may have only
fabrics often have damaged areas which are prone to been produced for a short period of time, and these
shedding. In addition, color-fading and discoloration cross-sectional shapes increase the significance
due to staining may allow a trace examiner to match of matching that type of fiber to a crime scene. For
evidence fibers to a source. Both plant or animal example, most carpet fibers exhibit a characteristic
fibers are commonly used to make fabric, and a given tri-lobal cross-section and can, therefore, be easily
fiber will possess a number of individual characters, identified using this technique. As with natural made
defined as qualities or features, that distinguishes fibers, the color of man-made fibers plays a role in
one fiber from another. These characters include the the significance of a match. Often manufacturing
fiber’s source, length, and degree of twist, as well as companies use specific color combinations to dye
the processing techniques and color additives used materials, and matching these unique colors with
during manufacturing. These individual characters, a fiber found at a crime scene can allow a trace
when taken together, may produce a complex profile analyst to determine the origin of the fiber.
of the questioned fabric.
Determining the significance of a similar fiber being
The most commonly used animal fiber in textile found at a crime scene and on a suspect’s clothing
manufacturing is wool. Wool fibers come from is a combination of evaluating the fiber’s defining
sheep and can vary in coarseness, which influences characters with the likelihood that the fibers could
the way it will be used in textiles. Finer woolen have been deposited on either location at random.
fibers are used in the production of clothing, while Finding multiple types of fibers on both suspect
coarser fibers are often reserved for the production and at the scene increases the likelihood that
of carpet. this did not occur by chance alone. Therefore, the
argument that the same fibers are found at both
The most abundant plant fiber used is cotton. places through coincidence is less convincing to
Because wool and cotton fibers are so common, a jury. In addition to multiple types of fibers, cross
the manufacturing characters (color, twist, weave) transfer of evidence is also highly significant. Cross-
add significance to any matches when they are transfer occurs when hair or fibers are exchanged
analyzed. Less common plant fibers include flax, between both the suspect and crime scene; that
jute, and hemp, and less common animal fibers is, the suspect leaves some fibers behind, while
include alpaca, camel, cashmere, and mohair. These taking some fibers away, from the scene. Such an
fibers offer a trace analyst increased significance exchange reduces the likelihood of a coincidence
and ease of match due to their relative rarity. and increases the significance of the findings

The majority of fibers used in textile manufacturing Because fibers are considered class, and not
are synthetic, or man-made. Some synthetic fibers individual, evidence, reporting matches between fibers

14 THE MYSTERY OF LYLE AND LOUISE