fiber analysis. introduction to fibers ■ trace evidence ■ class evidence ■ direct transfer:...
Post on 17-Dec-2015
223 Views
Preview:
TRANSCRIPT
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
top related