Fiber and Textile Forensic Science
Background Information
Mrs. Ashley
Name __________________________________________________
In this lab you will be identifying common weave patterns, compare and contrast various types
of fibers through physical analysis and apply forensic science techniques to analyze fibers
Vocabulary
1. Natural fiber: a fiber produced naturally from plant, animal or mineral sources (silk, cotton,
hemp, animal fur)
2. synthetic fiber: made from a man-made substance such as plastic (rayon, polyester, nylon,
acrylic)
3. textile: a flexible, flat material made by interlacing yarns or threads
4. yarn: fivers that have been spun together
5. fiber: the smallest indivisible unit of a textile, it must be at least 100 times larger than wide
6. direct transfer: passing of evidence such as a fiber from victim to suspect or vise versa
7. secondary transfer: the transfer of evidence from a source such as a carpet to a person
(suspect) and ten to another person (victim).
Anyone who wears clothes, sheds fibers. Fibers are not specific to a specific person. Fibers
are a form of trace evidence. They may come from clothing, carpet, sweaters, hats, scarves,
gloves, insulation or rope. Fibers may be transferred by direct transfer or secondary transfer.
Fiber evidence is obtained with special vacuums, sticky tape and forceps.
Early collection is critical. Within 24 hours 95% of fibers may have fallen off the victim or
been lost form a crime scene. Only fibers you would not expect to find are investigated. The
value of fiber evidence depends on its uniqueness.
Forensic scientists will ask the following:
1. Type of fiber- How common or rare?
2. Fiber color and dye type
3. Number of fibers found? More fibers suggest more violence or a longer period of
contact
4. Textile-Where did the fiber originate from? Is it carpet, car upholstery, clothing?
5. Multiple fiber transfers more sources mean larger contact
6. What was the type of crime committed?
7. What is the time between crime and discovery of fiber?
Testing Fibers and Textiles
1. The color and shape of the fiber is identified
2. Polarizing Light Microscopy uses a microscope that has a special filter to look at the fiber
using specific light waves
3. Infrared spectroscopy emits a beam that bounces off the material and returns to the
instrument which gives the chemical composition of the fiber.
4. The weave pattern is examined as well as the thread count. Thread count is given in
threads per inch.
5. Different types of fibers are used for different purposes so the type of fibers gives an
indication as to where the fiber was from.
Fiber Classification
Naturally Occuring Fibers:
Animal Fibers:
Fur is not a textile. The skin is treated and the fur remains attached. This is used exclusively
for gloves and coats and as trim on some clothing.
Some hair is removed from the animal and twisted into a fiber or yarn. Examples are wool
from sheep, cashmere and mohair from goats, angora from rabbits, and hair from alpacas, llams
and camel. They are often loosely spun.
Silk is collected from the cocoons of the caterpillar, Bombyx mori. The caterpillars are
reared in captivity and each cocoon must be carefully unwound by hand. The fibers tend to be
very long and aren't often shedded.
Plant fibers
Plant fibers tend to be made from cellulose. They are not made from protein such as
animal fibers, which make them easy to tell apart. Cellulose will not dissolve in water. Plant
fibers are very resistant to damage from harsh chemicals. They are often short and become
brittle over time. The small pieces of fibers are common trace evidence at crime scenes.
Cotton: it is found in the seedpod of the cotton plant
Coir: it is from the husks of coconuts, is very strong and use to make doormats and baskets
Flax: is made from the stem and used to make linen. It is highly crystalline that resists
damage.
Hemp and jute are used to make rope, mats and handbags.
Sisal is used for making ropes, twines and netting.
Mineral Fibers: these are things such as asbestos, fiberglass
Synthetic or Man-made fibers
Half of the fibers used today are manmade.
Rayon: This is from cellulose and is generally smooth and silky in appearance.
Cellulose can be combined with other manmade chemicals such as acetate to form Capron
(used in high performance clothing), and Celanese (used in carpets)
Synthetic polymer fibers: Under the microscope they have very regular diameters. They do
not have any internal structures, but may be solid or hollow. They may be clear or translucent.
Polyester: It is used in many fibers and provides additional strength
Nylon: It is easily broken down by light and concentrated acid.
Acrylic: This has a light fluffy feel and tend to ball or pill easily.
Here is Information from the Kentucky State Police on Fiber and Fabric
Evidence
The trace analysis section is that section of the laboratory which examines evidence
that does not conveniently fit into the other classifications. Paint, glass, soil, and
fibers however, are the most common types of evidence which are included in trace
evidence, and each will be discussed. As can be concluded from the title, trace
evidence refers to the size and quantities of evidence that can be collected. Paint
chips, a few bits of glass, and soil stuck to shoes are examples. Sometimes relatively
large quantities are present but usually just trace amounts are available. Currently
most trace cases are worked by chemists in the Central Lab, but some regional labs
perform limited services in this area.
The Kentucky State Police Laboratory System has available Trace Evidence Kits to
help in the collection and preservation of trace evidence. These kits contain zip-lock
plastic bags for samples like soil, round metal "pillboxes" for small particles, paper
envelopes with folded paper packets, a scalpel for collecting evidence, and evidence
seals.
Fibers and Fabric
Fiber examination and fabric comparisons can be encountered in a variety of types of
criminal cases. This analysis is performed by a trace analyst.
Value.
Fiber identification can be a great value in most types of investigations
and prosecutions. Crimes such as murder, rape, accident
investigation, robbery and assault can have fiber evidence. Fiber
identification can sometimes give important investigation leads as well
as good evidence for the prosecution purposes after further analysis is
concluded.
Information Determined.
1. The type of fiber can be determined by microscopic, chemical,
or instrumental tests either when found individually or as part
of a fabric. Synthetics, like polyester, nylon, etc., constitute the
majority of fibers used in the U.S. today. Wools, camel hair,
and silk are examples of fibers from animal sources.
2. Cotton, linen, hemp fibers, and jute are examples of plant
fibers. The wood fibers in paper are also fibers of vegetable
origin. Asbestos is a mineral fiber.
3. Comparisons of fibers of the same type of material include the
presence of dyes and a number of microscopic features.
Comparisons can be made with fibers from a fabric to
individual fibers or from fibers removed from another piece of
fabric. A fiber match, however, constitutes only class evidence.
4. The weave pattern of fabrics can also be compared, and
sometimes, when a piece has been torn from a fabric, that
piece can be matched up with weave pattern and irregularities
of a mutual tear edge. This is a example of individual
characteristics.
5. Similarly, cordage (ropes, string, etc.) tears and cuts can be
matched if the ends are not too frayed or distorted.
6. Fabric impressions may be found in a number of situations. The
impression of a victim's garment may remain on the oil pan or
on another flat surface of a vehicle in an accident investigation.
Collection of Evidence.
1. Since fiber evidence is generally small in nature, care should
be taken to prevent loss or contamination.
2. Several methods could be used in the collecting of fiber
evidence: visual searches, alternate light sources and searches
with additional magnification.
3. Recovery of evidence should be the most direct but least
intrusive technique practical. This could include picking,
scraping, or vacuuming.
4. Wrap clothing or items to protect adhering fibers if collection is
to be done by laboratory personnel.
5. Known samples should also be submitted for comparison
purposes.
6. All items should be sealed and labeled for identification.