0. Fibers
“Wherever he steps, whatever he touches, whatever he leaves even unconsciously, will serve as silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool marks he leaves, the paint he scratches, the blood or semen he deposits or collects—all of these and more bear mute witness against him. This is evidence that does not forget.”
—Paul L. Kirk (1902 – 1970)
Forensic scientist
Who Killed Misty.
Part 2.

1. Fibers Class or individual evidence Have probative value
Are common trace evidence at a crime scene
Can be characterized based on comparison of both physical and chemical properties

2. What is important about fibers found at a crime scene?
Type
Color
Shape
# of fibers found
Textile it originated from (carpet/curtains)
Multiple fiber transfer
Type of crime being investigated
Time between crime and discovery of fiber

3. Collected by:
Sticky tape
Forceps
Special vacuums

4. Analyze fibers by using:
Infrared spectroscopy – bounces beam off
If multiple fibers are available-
Burn tests
Dissolving test (chemicals)

5. Fabric
Fibers are made of twisted filaments
2 types:

6. man-made synthesized or created from altered natural sources Animal
Plant
Mineral
man-made
synthesized or created from altered natural sources

7. Natural
Silk
Cotton
Wool
Mohair
Cashmere
Angora

8. Natural Fibers Animal Plant Minerals Made of protein (Hair and silk)
Made of cellulose
From seeds, fruit, stems, and leaves
Minerals
Not made from protein or cellulose
Fiberglass and asbestos

9. Cellulose Fibers
Where does cellulose come from?
Cotton—vegetable fiber; strong, tough, flexible, moisture absorbent, not shape retentive
Rayon(viscose)—chemically-altered cellulose; soft, lustrous, versatile
Cellulose acetate—cellulose chemically-altered to create an entirely new compound not found in nature.

10. Fiber Comparison
Can you tell the difference(s) between the cotton on the left and the rayon on the right?

11. Protein Fibers Where does the protein come from?
Wool—animal fiber coming most often from sheep, but may be goat (mohair), rabbit (angora), camel, alpaca, llama, vicuna
Silk—insect fiber that is spun by a silk worm to make its cocoon; fiber reflects light and has insulating properties

12. Spider Silk

13. Kendall/Hunt Publishing Company
Kendall/Hunt Publishing Company

14. Kendall/Hunt Publishing Company
Kendall/Hunt Publishing Company

15. Mineral Fibers
Where do minerals come from?
Asbestos—a natural fiber that has been used in fire-resistant substances
Rock wool—a manufactured mineral fiber (insulation)
Fiberglass—a manufactured inorganic fiber

16. Synthetic
Rayon
Nylon
Acetate (taffeta)
Acrylic
Spandex
Polyester

17. Synthetic Fibers (Made from derivatives of petroleum, coal and natural gas)
Nylon—most durable of man-made fibers; extremely light weight
Polyester—most widely used man-made fiber
Acrylic—provides warmth from a lightweight, soft and resilient fiber
Spandex—extreme elastic properties

18. About half of the fibers are synthetic Two types 1. Regenerated fibers
Modified natural fibers
Example – rayon
2. Polymers
Made from petroleum products
No definite shape or size
Examples – acetate, nylon, acrylics, polyesters

19. Kendall/Hunt Publishing Company
Kendall/Hunt Publishing Company

20. Yarn
Fibers can made into yarn – twisted around each other – can analyze twisting pattern.
Yarn is then weaved into Textiles (material/cloth)
It is weaved into different patterns that can be used for identification.

21. Fabric Production
Fabrics are composed of individual threads or yarns, made of fibers, that are knitted, woven, bonded, crocheted, felted, knotted or laminated.
Most are either woven or knitted. The degree of stretch, absorbency, water repellence, softness and durability are all individual qualities of the different fabrics.

22. Weave Terminology Warp—lengthwise yarn (attached to beam)
Weft—crosswise yarn
Blend—a fabric made up of two or more different types of fiber.

23. Plain Weave The simplest and most common weave pattern
Design resembles a checkerboard
The warp and weft yarns pass under each other alternately
Examples – Cotton, chiffon, organza, and taffeta

24. Twill Weave Design resembles stair steps
Makes a diagonal weave pattern
Denim is one of the most common examples (chino and tweed)
The warp yarn is passed over one to three weft yarns before going under one

25. Satin Weave The yarn interlacing is not uniform Creates long floats
Interlacing weave passes over four or more yarns
Satin is the most obvious example

26. Weave Patterns
Plain
Satin
Twill

27. Weave Patterns

28. Knitted Fabric Interlocking loops into a specific arrangement.
It may be one continuous thread or a combination.

29. Filament Cross-Sections
Synthetic fibers are forced out of a nozzle when they are hot, and then they are woven. The holes of the nozzle are not necessarily round; therefore, the fiber filament may have a unique shape in cross-section.

30. Testing for Identification
Microscopic observation
- Color--compositional differences in the dyes
- Fibers surface--delustering particles that may be added by manufacturers
Burning—observation of how a fiber burns, the odor, color of flame, smoke and the appearance of the residue
Thermal decomposition—gently heating to break down the fiber to the basic monomers
Chemical tests—solubility and decomposition

31. Dyes
Components that make up dyes can be separated and matched to an unknown.
There are more than 7000 different dye formulations.
Chromatography is used to separate dyes for comparative analysis.
The way a fabric accepts a particular dye may also be used to identify and compare samples.

32. What is the function of fiber evidence?
With trace evidence, an investigator usually cannot say that one piece of evidence definitely originated from a specific item.
The investigator can only tell the jury what similarities were found and give them an idea of how rare those similarities are.
The Forensic Scientist’s main objective is to give the jury an idea about how rare the category is.

33. Fiber Evidence
Fiber evidence in court cases can be used to connect the suspect to the victim or to the crime scene.
In the case of Wayne Williams, fibers weighed heavily on the outcome of the case. Williams was convicted in 1982 based on carpet fibers that were found in his home, car and on several murder victims.
Although this case is unusual, fibers are generally considered of greater value as evidence than that of rootless hairs since they may contain a greater number of variables, thus showing more individual characteristics.

34. Kendall/Hunt Publishing Company

35. Man, I was nailed when those forensic guys found fibers
from the kid’s math assignment in my teeth.

36. Pollen Samples Are unique to each species
Vary in appearance, size and color
Can last unchanged for extended periods of time

37. Match suspect with crime scene
Any residue found to be a match
on clothing, shoes, or person
could place suspect at the scene
Flower
Pine tree

38. All pollen is unique

39. You can identify the type of plant and maybe its location by its pollen

40. Magdeberg, Germany Case London, Reuters 30 Sept. 1998
32 skeletons discovered in a mass grave in eastern Germany were either killed by the Gestapo in the spring of 1945 or by Russian secret police putting down a German revolt in the summer of 1953
Pollen evidence showed summer blooming oak, plantain, and grasses indicating that the bodies were Russian troops that were executed by the Russian secret police for refusing to fire on German civilians

41. Beach and River Sands

42. X-Ray Diffractometer For Mineral Identification
Kendall/Hunt Publishing Company

43. Polymers
Synthetic fibers are made of polymers which are long chains of repeating chemical units.
The word polymer means many (poly), units (mer).
The repeating units of a polymer are called monomers.
By varying the chemical structure of the monomers or by varying the way they are joined together, polymers are created that have different properties.
As a result of these differences, forensically they can be distinguished from one another.

44. More about Fibers
For additional information about fibers and other trace evidence, check out Court TV’s Crime Library at: