1. FIBERS

2. Locard’s Exchange Principle
When a criminal comes in contact with an object or person, a cross-transfer of evidence occurs.
Suspect may transfer evidence to scene or pick up evidence from scene

4. Cases involving fibers
Any physical struggle between two people
Carpet fibers adhering to shoes
Hit and run - pedestrian fibers on suspect vehicle
More fiber associations, more concrete the evidence
Primary and Secondary Transfer

7. Types of Fibers Natural Fibers Man-made Fibers (synthetic)
derived from animal, plant or mineral sources
Man-made Fibers (synthetic)
manufactured from raw materials or synthetic chemicals

8. What type of fibers are these?

9. Natural Fibers Broken into 3 classifications Animal fibers
Silk, sheep (wool), goats (mohair, cashmere), camels, horse, rabbits
Vegetable Fibers
Cotton, hemp, jute, ramie, flax, linen
Mineral Fibers
asbestos

10. Cotton Most prevalent natural fiber!!
White cotton fibers have no evidentiary value
Cotton jean fibers have little to no evidentiary value
Microscopic appearance: Ribbon-like shape with irregular twists

11. White Cotton Fibers

12. Man-made Fibers
Regenerated Fibers – produced from the naturally occurring polymer, cellulose
Cellulose = repeating units of glucose
rayon
Acetate
Triacetate

13. Man-made Fibers (continued)
Synthetic Fibers - produced from synthetic chemicals (polymers)
Nylon
Polyesters
Acrylics

14. Polymers Basic chemical substance of all synthetic fibers
Assumes different chemical and physical properties
Macromolecules of thousands to millions of atoms
Huge chains of repeating monomers
Natural polymers also exist

15. Synthetic Fibers have a very uniform appearance

16. Collection of Fiber Evidence
Post-It notes and paper packets (individual or small numbers of fibers
Tape Lifts cover large areas (i.e.. Care seats, victim’s clothing, etc.)
ALWAYS collect known samples (if several different carpets in the scene, collect a known from each one)
Package items separately to avoid cross-contamination

17. Natural vs. Synthetic Thru the Microscope
Natural fibers
Usually have a “twisty” appearance
Variable diameter
NO delustrant particles
Scales and medulla (animal hairs)
Cross hatching
Synthetic fibers
Smooth edges, lengthwise striations
Consistent diameter (usually)
Very clear or has delustrant particles

18. Single Fibers Collected onto a Post-It Note

19. Tape Lifting for Mass Collection of Fibers

20. Tape Lifts for Mass Collection of Fibers
White Background
Black Background