1. Fibers and Textiles

2. Fibers as Evidence
Fibers provide circumstantial or indirect evidence that can link a suspect to a crime scene
Example: a thief may own a jacket that matches fibers found at a crime scene
Fibers are considered class evidence since they are not specific to a single person
Most fibers are small or found in small amounts so they also are considered trace evidence

3. Checkpoint Classify fibers as…
Direct or circumstantial (indirect) evidence
Individual or class evidence

4. Fibers as Evidence
Fibers may originate from carpets, clothing, linens, furniture, insulation, or rope ect…
Fibers naturally shed from these items
Fibers are easily transferred or “picked up”
Fibers may be transferred from a victim to a suspect, this is called direct transfer
Example: Fibers from victim’s sweater found on suspect
If fibers are picked by victim and then transferred to suspect it is called secondary transfer.
Example: Victim picks up fibers from his/her couch earlier in day and then transfers to the suspect later

5. Checkpoint
Explain the difference between direct and secondary transfer

6. Time is of Essence
Early collection of fibers in an investigation is critical
Within 24 hours an estimated 95% if all fibers may have fallen off a victim or been lost from a crime scene
Only fibers not expected to be found at a crime scene are investigated

7. Something to Ponder
Police no longer cover dead bodies with cotton sheets at a crime scene. Why?

8. The Value of Fibers
The value of fiber evidence in an crime investigation depends upon its potential uniqueness
Example: a white cotton fiber has less value than an orange wool fiber

9. Not just Your Pets Shed! Textile Shedding
The most common form of fiber transfer to be encountered is the shedding of a textile
Textile (fabric) = a flexible, flat material made by interlacing yarns
Clothing, carpets, upholstery ect…
Fibers are short are spun into yarn or threads, individual fibers can there be pulled away or shed from fabrics (textiles)

10. Weave Pattern Yarns and fibers are woven into textiles or fabrics
5 Major types of weave pattern for textiles
Plain
Basket
Satin
Twill
Leno
Warp and Weft
determines weave pattern
Warp = length wise fiber
Weft = crosswise (vertical fibers)

11. Weave Patterns PLAIN Plain Alternating warp and weft pattern
Single fibers

12. Weave Patterns BASKET Basket Alternating warp and weft pattern
Double fibers- 2 weft threads crossing to warp threads

13. Weave Patterns SATIN Satin
Wefts are woven over 3 or more warp threads at a time

14. Weave Patterns TWILL Twill
Weft is woven over 3 or more warps and then under one
Next row the pattern is shifted over one to the left or right by one warp thread

15. Weave Patterns LENO Leno Use two warp threads and a double weft thread
To adjacent weft threads cross over each other

16. Thread Count Thread Count
In addition to weave pattern, textiles or fabrics also differ in thread count
Thread Count = threads per inch
Example- bed sheets
Often 180,200,400 or even 600
Higher thread count = higher price

17. Composition of Fibers Fibers are polymers
Large molecules made of subunits or monomers
Plant fibers are made of cellulose
Cellulose is composed of glucose molecules linked together
Animal fibers are protein
Proteins are composed of amino acids linked together

18. Fiber Classification NATURAL/ANIMALS
Animal Fibers
Wool = sheep
Cashmere and mohair = goats
Angora = rabbits
Silk = caterpillar Bombyx mori
Alpacas, llamas, camels

19. Fiber Classification NATURAL/PLANTS
Plant fibers
Grouped by part of plant that they originate from
Seed
Fruit
Stem
Leaf ect…
Made of polymer cellulose which is made of glucose monomers
Absorbs water
Insoluble in water = does not dissolve in water
Resistant to damage from harsh chemicals
Fibers are usually 2-5 cm long
Become brittle over time
Often found as trace evidence at a crime scene

20. Fiber Classification NATURUAL/PLANTS
Seed
Cotton
Made of cellulose
Easily woven and dyed
Used extensively in clothing and household textiles, most common type of fiber in world
Low in forensic value since it is so common
Fruit
Coir
Coarse fiber obtained from the covering of coconuts
Somewhat waterproof
Commonly used for doormats and baskets
Stem
Flax is most common, forms linen
Hemp and jute are also stem fibers
Leaf
Manila
Sisal- ropes and twines

21. Fiber Classification NATURAL/MINERALS
Minerals-not made of proteins nor cellulose
Fiberglass
Short, very weak, and brittle fibers
Rolls of fiberglass are used for insulation
Asbestos
Long, thin, durable fibers
Used in building materials

22. Synthetic Fibers Manufactured Fibers
Manufactured or regenerated fibers = cellulose or wood pulp is dissolved and cellulose is extracted.
Cellulose is then chemically combined with acetate and sent through tiny holes called spinnerets to make fibers that can be woven into yarn
Examples = rayon, celanese (carpets), capron (high performance clothing

23. Synthetic Fibers Synthetic Polymer Fibers
Petroleum (oil) based fibers, non-cellulose
No internal structures yet may be solid or hollow
Stronger than natural fibers
Examples:
Nylon
Polyester
Acrylic
olefins

24. Collecting Fiber Evidence
Special vacuums
Sticky tape
forceps

25. Sampling and Testing Non destructive methods
Microspectrophotometry uses white light or infrared light and measures a fibers “true color by measuring wavelengths of light that are reflected
Polarized light- tool estimates reflective index (amount and angle of light reflected) of the fiber
Refractive index- uses light beams and measures degree in which light is bent as it travels through fiber
Scanning electron microscope- can scan the surface textiles or fabrics to examine how damage occurred

26. Sampling and Testing Destructive Methods Burn tests
Dissolving in various solvents

27. Burn Key