Forensic Science
Name: ______________________________________ Period: ______
A. Fibers as evidence
a. Fibers are one of the most frequently encountered types of physical evidence at
crime scenes.
b. Because textiles are ___________-produced, they are considered _____________
evidence. It is difficult to trace a fiber back to a _________________ source, yet fiber evidence is still
important evidence because it creates _______________ between victims, suspects, and locations.
c. Fibers can come from ___________________, coats, ________________, furniture, ________________,
bedding, _____________________, rope, etc.
d. Fibers may be transferred directly from victim to suspect or suspect to victim, this is called
_________________ __________________.
e. However, an individual may have fibers on them that they picked up from the _____________________
and then transfers to the other person during contact, this is called ______________________ transfer.
f. ________________ collection of fibers is critical; most fiber evidence ( _______ %) falls off or is lost
from a crime scene within _______ hours.
g. When using fiber as evidence, forensic scientists want to determine the following:
i. Type of fiber – composition and ________________________
ii. Fiber ________________– first step of matching fiber to location. Later, scientists can test to
see if ________________ used also match.
iii. ________________ of fibers found – usually the more found the easier the match. More fibers
also suggest more ___________________ crime or longer period of contact.
iv. Where the fiber was found – can you place the suspect at the scene or to the victim?
v. Textile fiber originated from – What is the ________________ of the fiber?
vi. Are there __________________ types of fibers – several types of fibers can be more supportive.
vii. Type of crime committed – If forensic scientists know the crime, they have a better idea of what
kind of fiber transfer to look for. Examples- ________________, ________________________,
breaking and entering, etc.
viii. Time between crime and fiber ______________________ – passage of time greatly reduces the
value of fiber evidence.
B. Collection of fibers
a. _____________________ search first.
b. Use of ___________________ or sticky ______________ for small areas.
c. ______________________ for larger areas.
d. Removed fibers should be folded into a paper __________________ or
in a ________________ envelope, which can be sealed and marked.
e. Each garment should be-laid on a clean sheet of paper, and separately rolled up in the paper. Bag
clothing items individually in paper bags. Make sure that different items are not placed on the
________________ surface before being bagged.
f. Recording where fibers were found is critical for evidence to be admissible in court.
g. ____________________ samples are important also. Known samples should be taken from all possible
sources for ______________________________.
C. Testing fibers
a. First identify the type of fiber and its characteristics using a _______________. Try
to identify the color, texture, diameter, shape pattern, cross section appearance,
etc.
b. If there is a _____________________ amount of fiber found at the crime scene, it
is important scientists do not perform tests that will _____________________ the
evidence.
c. Two nondestructive procedures are:
i. ________________________ light microscopy- allows scientists to look at
optical properties of the fiber using specific wavelengths of light.
ii. ___________________ _______________________- allows scientists to see chemical structure
of fiber using beams of light.
d. If ________________ quantities of fibers are found, _______________ of the fibers can be used for
more destructive procedures, which allow for more conclusive data.
i. ______________________- can compare melting points, odors, ash formation, etc.
ii. ______________________- can compare solubility
iii. ______________________- can compare absorption of various stains
iv. ______________________- often a quick way to classify fabric origins
v. ____________________________- gives a more detailed analysis of the dye composition
e. If fabric or cordage is found (many fibers still linked together) then scientists also look for a physical
__________________ (like puzzle pieces). They also can compare the __________________ of knit or
weave used.
D. Classification of fibers
a. Size / Terminology
Fiber  Yarn  Textile
i. A fiber is the ______________________ indivisible unit of a textile
ii. Fibers too short to be used to make textiles in their raw state may be ______________ together
to make ________________.
1. Any given yarn will have a ______________________ of twist. Forensic scientists will
identify the twist direction as part of their forensic identification process.
iii. Yarn is woven, with different ____________________, into ____________________
1. Weaving consists of arranging lengthwise threads (called the ________________ ) side
by side. Then crosswise threads (called the ________________ ) are woven back and
forth in one of many different patterns.
2. Weave patterns are determined by ___________________ of threads jumped as weave
over and under. Weave patterns vary and can be used as forensic evidence.
_____________


Simplest and most
_______________ weave
Warp and weft pass under
each other alternately
_____________

Create by passing the
warp yarn over three weft
yarns before going under
one
_____________

One weft crosses over
three or more warp
threads



Create even patterns of
1/1 and 2/2
Design resembles a
_____________________
Snag resistant but tends
to ___________________




Makes a
__________________
weave
Design resembles stair
steps
_________________ is the
most obvious example
Soft and pliable, yet strong



Interlacing may not be
uniform.
Shiny, little
__________________
with other garments.
Not durable; tends to
_________________ or
break
3. _________________ _________________is the number of threads that are packed
together for any given amount of fabric; it also varies and can be used as forensic
evidence.
b. Fibers may be _____________________ or ____________________
i. Natural fibers come from _____________________, ___________________, and mined
___________________.
ii. Synthetic fibers are ______________-made.
E. Natural fibers
a. Animal fibers
i. All animal fibers are made of _____________________.
ii. Animals provide fibers from 3 sources: __________, ____________, and ___________ webbing.
iii. Fur
1. Fur is a good donor of fibers, but not for textiles. Instead, fur is left on the skin and
treated, then used to make _______________ and gloves.
iv. Hair
1. Hair can be ___________________ out of an animal’s coat, _______________ naturally
and collected, or ____________________ off.
a. Sheep- _______________
b. Goats- _____________________, mohair
c. Rabbits- _________________
d. Alpacas, llamas, and camels
v. Silk
1. Silk comes from the _________________ of the
silkworm caterpillar, Bombyx mori.
2. Silk fibers tend to be very long and therefore do
not _______________ as easily as hair fibers.
b. Plant fibers
i. All plant fibers are made of ______________________, a _______________________ polymer.
ii. Plant fibers are grouped by the _________________ of the plant that they come from.
1. Seed- _________________
a. Most common plant fiber. If not dyed, it will not likely provide much forensic
evidence- too common.
2. Fruit- Coir (surrounding of a coconut)
a. Often used for ______________________ and baskets.
3. Stem
a. _________________ (Cannabis)- popular alternative to cotton
b. _________________- used in rope, mats, handbags, burlap sacks
c. flax- used in _________________
4. Leaf
a. ______________________, relative of the banana tree- used to make paper and
envelopes
b. Sisal, a desert plant- used to make ________________, twine, and netting.
c. Mineral fibers
i. Mineral fibers are __________________ protein nor cellulose.
1. ______________________- a fiber form of glass; used to
insulate buildings
2. ______________________- mineral found in rocks; used
mainly because of its _____________ resistance. Found
around pipes and fireplaces, in ceiling and floor tiles, fire
resistant cloth, shingles, home siding, and insulation.
a. Asbestos is known to cause ______________. When
broken we can inhale tiny fragments and damage the
lungs. ______________ tissue can then become cancerous.
F. Synthetic fibers
a. Half of the fabrics produced today are ___________-made, synthetic fibers.
b. Synthetic fibers are made of _____________________ which are long string of repeating chemical units,
called ____________________.
c. By varying the chemical structure of the monomers or by varying the way they are weaved together,
polymers are created that have different ________________________. As a result of these differences,
forensically they can be distinguished from one another and be used as physical evidence.
d. They can be broken down into two groups: _______________________ fibers and _________________
polymer fibers
e. Regenerated fibers
i. Cellulose esters-- These are derived from cellulose and produced by chemically ______________
the natural polymers to create an entirely new compound not found in nature. Examples:
1. ____________________- most common. first man-made fiber; soft, versatile.
2. ____________________- less expensive, less polluting than rayon.
f. Synthetic polymer fibers
i. Petroleum Plastics- these originate from derivatives of petroleum, coal and natural gas. They are
____________________ man-made. Example:
1. ____________________- most durable man-made fabric; extremely light weight. First
introduced as artificial silk for pantyhose.
2. ____________________- most widely used man-made fiber. Inexpensive and tends to
ball easily.
3. _________________________ -provides warmth from a lightweight, soft and resilient
fabric. Common in polar fleece and many wrinkle resistant pants.
4. ____________________- extreme elastic properties.
G. Comparison of natural and synthetic fibers
a. Synthetic fibers are much _____________________ than natural fibers.
b. Unlike natural fibers, synthetic fibers are not _______________________ by
microorganisms.
c. Synthetic fibers can deteriorate in bright __________ and melt at a
_________________ temperature than natural fibers.
d. Under magnification, all synthetic fibers have very regular
___________________________.
e. Hairs have a ____________________.
Activity: Find a partner and compare the fabric of your shirts. Then look at the tag inside your shirts. What are your
shirts made of? Did you expect this? ____________________________________________________________________
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