Fiber Analysis

Introduction to Fibers

■ Trace evidence■ Class evidence■ Direct transfer: suspect ←→ victim■ Secondary transfer: source → suspect

→ victim■ 95% of fibers lost from crime scene

within 24 hours

Forensic scientist determines:

■ Type of fiber – Natural vs Synthetic

■ Color

■ How many of each kind – Locard’s Principle

Forensic scientist determines:

■ Textile origin

■ Multiple types of Fibers

■ Transfers

■ Type of crime

Fiber EvidenceCollected by:■ Special vacuums (large areas)■ Sticky tape■ Forceps

Tested by:■ Microscopy – polarizing light,

infrared■ Burn test (large quantities only)

■ Fibers are spun into yarns that have specific characteristics

■ Fibers may be natural or synthetic

■ Yarns are woven, with different patterns, into textiles

Natural Fibers■ Animal fibers (protein)

■ Sheep – wool■ Goats – cashmere, mohair■ Rabbits – angora■ Caterpillar – silk

■ Plant fibers (cellulose)■ Seed: cotton■ Stem: hemp (Cannabis), jute, flax (linen)

■ Mineral fibers■ Fiberglass (glass) , asbestos (rock mineral)

WOOL

COTTON

FIBERGLASS

ASBESTOS

FLAX

JUTE

HEMP

SILK

Synthetic (Man-made) Fibers

■ Regenerated fibers (modified natural fibers)■ Rayon

■ Synthetic polymer fibers■ Polyester■ Nylon■ Acrylic