1. Textiles & 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

2. What is a fiber? A fiber is the smallest unit of a textile material.
A single strand
At least 100x longer than wide
Fibers can be natural or man-made.
A fiber can be spun or twisted with other fibers and be woven or knitted to form textiles.
I.e….carpet, clothing, upholstery, yarns

3. What Can Fibers Tell Us? Establish contact between two individuals
Establish contact between an individual and an object.
Value of fiber as evidence depends on
Type of fiber
Color or color variations in fiber
Number of fibers that matches between victim and suspect.
Location & source of fiber*

4. Primary transfer Secondary transfer
occurs when already transferred fibers on the clothing of a suspect transfers to clothing of a victim, or vice versa
I.e… the victim has carpet fibers on her clothing which are then transferred to the suspected rapist
AKA direct transfer
occurs when fibers are transferred from a victim directly onto a suspect, or vice versa
I.e… wool fibers from a rapist’s sweater are transferred the victim’s shirt
*Whether a collected fiber is the result of primary or secondary transfer is a key factor in reconstructing a crime scene.

5. Fibers Are … considered class evidence
common trace evidence at a crime scene
characterized based on comparison of both physical and chemical properties

6. Two fiber classifications
Chapter 6
NATURAL
SYNTHETIC
Man-made textiles
Artificial—synthesized or created from altered natural sources
Naturally produced
Animal fibers
Plant fibers
Mineral fibers
*NOT inorganic necessarily
Two fiber classifications
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7. Animal Fibers Protein –based Fur NOT a textile Attached to skin Hair
Chapter 6
Animal Fibers
Protein –based
Fur
NOT a textile
Attached to skin
Hair
Most common animal fiber
I.e… wool, cashmere, mohair, angora, camel hair
Webbing
Silk
Made from the cocoons of Bombyx mori caterpillar which are unwound by hand
4 minute video on where silk comes from & how its made
Silk made from unravelled silkworm cocoons (soaked in water loosen)
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8. Plant Based Fibers are…
Composed of cellulose
A glucose polymer
Insoluble in water
Short
Classified based on what part of the plant they are made from

9. Most common plant textile Made from seed-pod of cotton plant
Chapter 6
COTTON
SEED based fiber
Most common plant textile
Made from seed-pod of cotton plant
Used to make clothing & household textiles
COIR
FRUIT based fiber
Made from coconut husks
Used to make doormats, baskets
Flax also known as linen…. A STEM fiber
*Hemp/flax & jute grown in bundles as opposed to individual fibers like cotton (Hemp can be 6+ foot tall)
LEAF fibers – sisal as in sisal rugs
HEMP
STEM based fiber
Made from a tall species of Cannabis
Grow in long bundles*
Used for clothing textiles
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10. Mineral-based fibers ASBESTOS FIBERGLASS Long, thin fibrous crystals
Chapter 6
ASBESTOS
Long, thin fibrous crystals
Fire resistant
Shingles, brakes, ceiling tiles
FIBERGLASS
Short, weak & brittle fibers
Fibrous form of glass
Insulation
Mineral-based fibers
Asbestos – car brake linings, fireproof clothing
****cancer causing agent with inhalation – extreme car to remove from old homes & skin irritant
Fiberglass – skin irritant w contact
***** cigarettes used to contain fiberglass fibers to allow nicotine to more easily penetrate lungs & increase addiction (rumored to, at least)
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11. Chapter 6
So how would you go about distinguishing a plant fiber from an animal fiber?
Look for CUTICLE pattern & medulla
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12. Fiber Comparison Can you tell the difference(s) between the cotton on
the left and the rayon on the right?
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13. Synthetic Fibers > half of fibers produced
Chapter 6
Synthetic Fibers
> half of fibers produced
Made from recycled plastic, derivatives of petroleum & coal
Formed by process of melting and extrusion
How Its Made video clip….4 minutes but they get the idea by 2:30
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14. Synthetic Fibers Include….
POLYESTER
Strong, resistant fabric
Most abundant sythetic
polar fleece & wrinkle-free clothing
NYLON
ACRYLIC
Light and fluffy
Imitation fur
inexpensive
OLEFINS
Quick-dry fabrics
‘high-performance’ clothes
Carpets
STURDY
Synthetic Fibers Include….

15. Natural vs Synthetic Fibers
Chapter 6
NATURAL FIBERS
SYNTHETIC FIBERS
Irregular diameters
Cuticle & medulla*
Inconsistent pigmentation
Varied texture
Straight, curly
Rough, uneven edges
Dull or lustrous
Uniform diameter
Lack cuticle & medulla
Uniform pigment
Generally straight or slightly curved
Smooth, even edges
Lustrous
*animal fibers
Synthetics are treated with chemicals that make them shiny
Natural vs Synthetic Fibers
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16. Natural or Synthetic?

17. Chapter 6
Coarse wool > fine wool > alpaca > cashmere > silk > linen > Cotton > polyester
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18. Chapter 6
Wool fiber(cuticle, medullary index, nonuniform diameter) Alpaca (non uniform diameter & color, medulla)
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19. Testing for Identification
Microscopic observation
Burning—observation of how a fiber burns, the odor, color of flame, smoke and the appearance of the residue
Thermal decomposition—gently heating to break down the fiber to the basic monomers
Chemical tests—solubility and decomposition
Testing for Identification
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20. Dyes
Components that make up dyes can be separated and matched to an unknown.
There are more than 7000 different dye formulations.
Chromatography is used to separate dyes for comparative analysis.
The way a fabric accepts a particular dye may also be used to identify and compare samples.
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