Forensics Unit 2 Notes
Chapter 6 – Fibers
Fibers- usually made up of many filaments twisted or bonded together to form a thread or yarn
Textiles- fabrics woven in a distinctive pattern (bonded textiles such as felt lack a pattern)
I.
Fibers as Evidence
a. Like hair fibers are one of the most common items left at a crime scene
b. Have probative value b/c they create connections or associations. (class evidence)
II.
Fiber Sources
a. Filaments- single strands of material, usually twisted with other filaments to make a thread or
fiber.
b. Fabric- material made up of fibers woven or bonded tighter in a distinctive manner
c. Filaments are twisted to make the fiber and the fiber is woven to make a fabric
d. Types of fibers
i. Synthetic- man made
1. EX: Rayon, Nylon, Acetate, Acrylic, Spandex, Polyester
ii. Natural- from plants or animals
1. Cellulose- plant – Cotton, Jute, Hemp…
2. Protein- Animal – Wool, Cashmere, Silk, Mohair
3. Mineral- fibers made by man using natural ingredients – fiberglass, asbestos
e. Fibers are woven into fabrics
i. Yarn - strand of fibers
ii. Warp - lengthwise yarn or thread in a weave
iii. Weft or Woof - the crosswise yarn
iv. Blend - warp and weft not the same types of fiber
v. Weave patterns
1. plain checkerboard (alternate over-under)
III.
2. twill
stair-steps (over, under 3)
3. satin
obvious (over, under 4 or more)
4. knitted complex weave of fabric
Fiber Morphology
a. Fiber cross section- shapes vary, especially synthetic
b. Chemical Structurei. Polymers- (poly)- Many, (mer)- Units
ii. Helix- spiral arrangement
knitted