Fiber Analysis

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Fiber Analysis

• Miss Stanley
• Middle School Science Club
• Forensic Division

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Textile Fiber
A textile fiber is the basic unit or building
block of a fabric. Fibers are produced naturally
by plants and animals and synthetically by man.
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3 Basic Fiber Categories

• Natural
• Manufactured, or regenerated
• Synthetic

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Natural Fibers
Come from various animals, plants, and minerals.
Examiners can often easily identify and compare
these fibers by microscopic inspection alone.
Animal hair that is woven into fabric or used to
manufacture clothing and other household items is
considered natural fiber.
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Natural Fiber - Cotton
By far, the most commonly used natural fiber is
cotton. When examined under a microscope, it has
an easily recognizable twisted-ribbon pattern.
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Natural Fiber - Wool
The most common animal fiber used in textile
production is wool originating from sheep.
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Natural Fibers
Other examples are mohair, cashmere, and silk.
Plant fibers include cotton, hemp, flax, and
jute.
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Manufactured or Regenerated Fibers
Are fabrics like rayon, acetate, and triacetate.
To make them, raw cotton or wood pulp is
dissolved, and cellulose is extracted. The
cellulose is then regenerated into fibers.
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Synthetic Fibers
Come from polymers, which are substances made up
of a series of monomers (single molecules) strung
together to make larger molecules that can be
thousands of monomers long. Nylon and polyester
are synthetic fibers.
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Textile Definitions

• Fiber is smallest unit of a fabric.
• Fibers are twisted into yarns.
• Yarns are knit or woven into fabrics.
• Known or Standard fibers make up fabric of a
  donor or source garment.
• Question or Transferred fibers are found on or
  recovered from (the debris from) a receptor
  garment.

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Fiber Evidence
A fiber is the smallest unit of a textile
material that has a length many times greater
than its diameter. A fiber can be spun with other
fibers to form a yarn that can be woven or
knitted to form a fabric. The type and length of
fiber used, the type of spinning method, and the
type of fabric construction all affect the
transfer of fibers and the significance of fiber
associations. This becomes very important when
there is a possibility of fiber transfer between
a suspect and a victim during the commission of a
crime.
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Fiber Evidence
Matching unique fibers on the clothing of a
victim to fibers on a suspects clothing can be
very helpful to an investigation, whereas the
matching of common fibers such as white cotton or
blue denim fibers would be less helpful. The
discovery of cross transfers and multiple fiber
transfers between the suspect's clothing and the
victim's clothing dramatically increases the
likelihood that these two individuals had
physical contact.
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Natural Fibers
Many different natural fibers that come from
plants and animals are used in the production of
fabric.
Cotton fibers are the plant fibers most commonly
used in textile materials
The animal fiber most frequently used in the
production of textile materials is wool, and the
most common wool fibers originate from sheep.
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Textiles Fibers as Evidence

• Crimes Against Persons
• Homicide, Assaults, Sex Crimes - used to indicate
  contact by transfer of fibers between V and S
  clothing, transfer of fibers between V/S and
  scene.

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Textiles Fibers as Evidence

• Crimes Against Persons
• Indication of Force in Crimes Against Persons -
  rips and tears.
• Sabotage - cut or tied parachute lines.

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Textile Fibers as Evidence

• Crimes Against Property.
• Burglary, Larceny, - torn fabric or loose fibers
  at point of entry, fabric marks from gloves,
  fibers from the scene transferred to suspect.

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Factors Influencing Transfer and Persistence

• Studies show within 2 hours of transfer, 80 of
  fibers are gone.
• Fiber type.
• Weave or knit type.
• Damage to the garment or fabric.
• Amount or force of contact.
• Garments vs. automobiles.

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Laboratory Examinations

• Color - Dyes
• Size - Diameter
• Cross Sectional Shape
• Transparent or Opaque
• Chemical Composition

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Fiber Reports / Conclusions

• How common is the fiber?
• How many were found?
• Is there a combination of fibers? (Consistent
  with one garment or one set of clothing?

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Laboratory Tests Well Do

• Burning Characteristics
• Solubility
• Staining
• Microscopic Appearance