1. Analysis of Fiber Evidence

2. Types of Fibers
Cotton
Natural Fibers: fibers derived entirely form animal or plant sources.
Majority of fiber evidence found at crime scene is animal fiber.
Examples: sheep (wool), goat (mohair/cashmere), camel, llamas, alpacas, and vicunas.
Uses same forensic procedures as determination of species hair analysis.
Predominant plant fiber is cotton.
Most distinguishing feature – ribbon-like shape with twists at irregular intervals.
Has almost no evidential value. Why?
Wool

3. Types of Fibers
Manufactured: fibers derived from either natural or synthetic polymers.
First man-made fibers:
1911 – Rayon
Nylon
Hard to distinguish between fibers due to large number of sub names. Confusing system.
Ex. Polyester is also known as
Dacron
Fortrel
Kodel
Classified as generic fibers

4. Natural vs. Man-made polymers
Regenerated Fibers: derived from cotton or wood pulp.
Process
Cellulose is extracted and sometimes chemically altered.
Forced through sinning jet/spinneret to create fiber.
Synthetic Fibers: chemically created.
Formed from long chain molecules called polymers.

5. Polymers
Substance composed of a large number of atoms that are usually arranged in repeating units called monomers.
Ex. Plastic, paint, adhesive, synthetic rubber
Referred to as macromolecules.
Ex. Linking blocks.

6. Polymers
Polymerization: covalently bonded monomers that create long repeating subuntis.
Nylon 6,6 is an example of a polymeric clothing material, involving one of each monomer, hexamethlene diamine and adipic acid, that react to form Nylon 66.

7. Identification and Comparison of Manufactured Fibers
Microscopic Examination:
1st step – comparison of color and diameter.
A cross sectional view of fiber may be helpful.
Then need to look at mixture of dyes selected to create certain shade of fiber.
Other Techniques (Analytical)
Chemical Composition
Nylon 6 vs. Nylon 6,6
Birefringence
Difference in the two indices of refraction exhibited by most crystalline materials.
Infrared Absorption
Absorption of infrared light in a particular pattern.

8. NYLON 6 VS. Nylon 6,6

9. Collection and Preservation
Articles of clothing should be placed in separate paper bags.
Carpet, rugs, and bedding are to be folded carefully to protect areas suspected of containing fibers.
Wrap knife blades that may contain fibers
Remove fibers from body using adhesive tape.
Loose fibers are to be removed with a clean forcep and placed in a small sheet of paper, which once folded and labeled can be placed inside another container.

10. Atlanta Child murders – Wayne Williams