1. Fiber and Textile Evidence
Ms Clark
PVMHS

2. Fibers are used in forensic science to create a link between crime and suspect

3. If fibers from one person’s clothing were found on a murder victim, does this evidence prove that this person committed the crime?
Why or why not?

4. Example:
A thief owns a jacket made of a material that happens to match the type of fiber found at the crime scene.
This does not mean that he was there, but a jacket like his was.

5. Example:
A thief owns a jacket made of a material that happens to match the type of fiber found at the crime scene.
This does not mean that he was there, but a jacket like his was.
If a jacket fiber, sock fiber, and shirt fiber all from the items the thief owns are found at the crime scene, then the chances they were present are higher or increased.

6. What type of evidence are fibers?
Trace evidence?
Direct or circumstantial?
Class or Individual?
Physical or Biological?

7. What type of evidence are fibers?
Trace evidence?
Yes
Direct or circumstantial?
Class or Individual?
Physical or Biological?

8. Fiber Transfer Direct transfer Secondary transfer
Fibers transferred directly from victim to suspect or suspect to victim
Secondary transfer
Victim picks up fibers, then transfers them to suspect
Fibers are transferred from original source to suspect and then to the victim or crime scene

9. Fiber Transfer Example of direct transfer
Fiber from suspect’s shirt transfers onto victim
Example of secondary transfer
Fiber from carpet at suspect’s home transfers onto his shirt, then transfers onto victim

10. Fiber Collection Early collection is critical
Within 24 hours, an estimated 95% of all fibers may have fallen from a victim or been lost from a crime scene
Only collect fibers that are unexpected
Ex: Victim has a pink carpet at home, don’t collect pink fibers

11. Considerations by Forensic Scientists
Type of fiber
Fiber color
Number of fibers found
Where fiber was found
Type of crime committed
Time between crime and discovery of fiber

12. Using your book, elaborate on each of these considerations and add to your notes additional questions to follow up these initial considerations.

13. Fiber Collection Special vacuums Sticky tape Forceps
Important to be very accurate in recording where fibers were found
Incomplete or inaccurate recording may cause evidence to be inadmissible in court

14. Fiber Analysis Identify type of fiber and characteristics
Color, shape
Match to fibers from a suspect source (car, home)
If only one fiber is obtained, only tests that will not damage or alter the fiber can be used
Polarizing light microscopy, infrared spectroscopy

15. Fiber Analysis Polarizing Light Microscopy Infrared spectroscopy
Allows scientist to observe fiber at specific wavelengths
Infrared spectroscopy
Emits a beam that bounces off the material then returns
How the beam of light has changed reveals details of the chemical structure of the fiber

16. Fiber Analysis
If large quantities are obtained, some fibers may be subjected to simple, but destructive testing
Burning in flame
Dissolving in liquid

17. Fiber Types Textiles Most common form of fiber transfer
Clothing, carpets, upholstery
Constructed by weaving yarns
Arranging lengthwise threads (the warp) then weaving crosswise threads (the weft) into different patterns
This is called the “weave pattern”
Types of weave patterns: tabby, twill, satin

18. Weave patterns
Using page 86 in your book, fill out your “weave patterns” table.
Draw a diagram of each one

19. Fiber Types Yarns Made up of fibers that have been “spun” together
“Twist” direction is used as part of identification

20. Fiber Classification Natural fibers Synthetic fibers
Come from animals, plants, minerals
Synthetic fibers
Man-made fibers

21. Natural Fibers Animal fibers Plant fibers
3 sources: hair, fur, webbing
Made of proteins
Ex: Fur coats, wool from sheep used in textiles, silk
Plant fibers
Specialized plant cells
Sources: seeds, fruits, stems, leaves
Made of cellulose
Ex: Cotton

22. Plant Fibers Seed fibers Fruit fibers Stem fibers Leaf fibers
Cotton is found at the seed of the cotton plant
Fruit fibers
Coir is a coarse fiber obtained from the covering of coconuts
Stem fibers
Hemp, flax
Flax is most common – found in linen
Leaf fibers
Manila is a fiber extracted from abaca leaves (relative of banana tree)
Other leaf fibers used to make ropes, twines, netting

23. Natural Fibers
Mineral fibers
Fiberglass
Asbestos

24. Synthetic (man-made) Fibers
Regenerated fibers (modified natural fibers)
Derived from cellulose
Mostly plant in origin
Ex. Rayon
Polymer fibers
Originate from petroleum products
Easy to distinguish between synthetic fibers in lab
Ex: Polyester (found in fleece, wrinkle resistant clothes), Nylon, Acrylic (imitation wool), Olefins (thermal socks and carpets)

25. Natural vs Synthetic Fibers
Synthetic fibers are stronger than natural fibers
Synthetic fibers are not damaged by microorganisms
Synthetic fibers can deteriorate in sunlight
Synthetic fibers melt at lower temperatures than natural fibers

26. Appearances of Common Fibers under Microscope
Using page 84, determine what fiber each characteristic belongs to. Copy it down in your table.

27. Summary Class evidence and trace evidence
Scientists try to determine type of fiber, its color, how many if each fiber were found, what textile the fiber came from, whether there were transfers of multiple types of fibers
May be gathered using special vacuums, sticky tape, or tweezers

28. Summary
Analyzed using polarizing light microscopy, infrared spectroscopy, burn tests, solubility tests
May be natural or synthetic
Natural: animal hair, plant fibers from seeds, fruit, stems, or leaves, and mineral fibers
Synthetic: Regenerated or modified natural fibers and polymer fibers
Spun into yarns with specific characteristics
Yarns are woven into textiles with different patterns