Chapter 6: Fibers “Wherever he steps, whatever he touches, whatever he leaves even unconsciously, will serve as silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool marks he leaves, the paint he scratches, the blood or semen he deposits or collects— all of these and more bear mute witness against him. This is evidence that does not forget.” —Paul L. Kirk (1902 – 1970) -Forensic scientist
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Chapter 6: Fibers
“Wherever he steps, whatever he touches, whatever he leaves
even unconsciously, will serve as silent witness against him. Not
only his fingerprints or his footprints, but his hair, the fibers from
his clothes, the glass he breaks, the tool marks he leaves, the
paint he scratches, the blood or semen he deposits or collects—
all of these and more bear mute witness against him. This is
evidence that does not forget.”
—Paul L. Kirk (1902 – 1970)
-Forensic scientist
Chapter 61
Fibers
How fibers can be used
as circumstantial
evidence to link the
victim, suspect, and
crime scene.
Why fibers are class
evidence.
Why statistics are
important in determining
the value of evidence.
The student will learn:
Students will learn:
Chapter 62
Fibers
Are considered class evidence
Have probative value
Are common trace evidence at a
crime scene
Can be characterized based on
comparison of both physical
and chemical properties
Chapter 63
Fibers at the Crime Scene
Can occur
When two people come in contact
When contact occurs with an item from the crime scene
Methods of transfer
Direct transfer — fiber transferred from fabric directly onto victim or suspect
Indirect transfer — fibers already transferred onto clothing of suspect or victim transfer onto the other party
Chapter 64
Forensics of Fiber Analysis
Cross transfers of fiber often occur in cases in
which there is person-to-person contact
Investigators hope that fiber traceable back to
the offender can be found at the crime scene,
as well as vice versa.
Success in solving crimes often hinge on the
ability to narrow the sources for the type of
fiber found, as the prosecution did with their
probability theory on the fibers
Chapter 65
Fiber Evidence
Fibers are gathered at a crime scene with
tweezers, tape, or a vacuum.
They generally come from clothing,
drapery, wigs, carpeting, furniture, and
blankets.
For analysis, they are first determined to
be natural, manufactured, or a mix of
both.
Chapter 66
Collection of
Fiber Evidence
Bag clothing items individually in paper
bags. Make sure that different items are
not placed on the same surface before
being bagged.
Make tape lifts of exposed skin areas of
bodies and any inanimate objects
Removed fibers should be folded into a
small sheet of paper and stored in a
paper bag.
Chapter 67
Fiber Evidence
Fiber evidence in court cases can be used to connect the suspect to the victim or to the crime scene. In the case of Wayne Williams, fibers weighed heavily on the outcome of the case. Williams was convicted in 1982 based on carpet fibers that were found in his home, car and on several murder victims.
Chapter 68
Fiber Evidence
The problem with fiber evidence is that fibers are not unique.
Unlike fingerprints or DNA, they cannot pinpoint an offender in any definitive manner.
There must be other factors involved, such as evidence that the fibers can corroborate or something unique to the fibers that set them apart.
Chapter 69
Fabric
Fabric is made of fibers. Fibers are
made of twisted filaments
Types of fibers and fabric
Natural —animal, vegetable or
inorganic
Synthetic (Artificial) —synthesized
or created from altered natural
sources
Chapter 610
Types of Fibers
Synthetic
Rayon
Nylon
Acetate
Acrylic
Spandex
Polyester
Natural
Silk
Cotton
Wool
Mohair
Cashmere
Chapter 611
Identification of Fibers
Plant (vegetable) fibers are
characterized by anatomical features.
Animal fibers are recognized by their
morphology and classified into major
groups.
Synthetic and regenerated fibers are
characterized by polarized light
microscopy.
Chapter 612
Fiber Comparison
Can you tell the difference(s) between the cotton on
the left and the rayon on the right?
Chapter 613
Classification
Natural fibers are classified
according to their origin:
Plant fibers Animal fibers Mineral fibers
Chapter 614
Classification of fibers by
their compositionNatural plant fibers may be more ribbon
shaped and may contain twists at irregular intervals
Natural fibers from an animal source look like hair and will often have rough external scale patterns and medulla
Synthetic fibers tend to be smooth and uniform and some may have long striations lines on the other layer