1. Textiles and Fibers
Forensic Science: Fundamentals & Investigations, Chapter 4

2. A Study of Fibers and Textiles you will be able to:
identify and describe common weave patterns of textile samples
compare and contrast various types of fibers through physical and chemical analysis
describe principle characteristics used to identify common fibers
apply forensic science techniques to analyze fibers

3. Introduction and How Forensic Scientists Use Fibers
How are fibers used in Forensic Science?
To create a link between crime and suspect or to
Fibers are not specific to an individual, but…
often fall off and are picked up during activities and go unnoticed
may provide police with evidence even if a suspect wears gloves
Fibers are a form of trace evidence
Where can fibers originate?
Forensic Science: Fundamentals & Investigations, Chapter 4

4. Textile Fiber Defined
Defined as the smallest part of a textile material
Many objects in our environment (clothing, ropes, rugs, blankets, etc.) are composed of yarns made of textile fibers

5. Textile Fiber Categories
Animal (hairs)
Wool, cashmere, silk
Vegetable
Cotton, kapok, linen
Mineral
Asbestos
Manmade
Acetate, rayon, nylon, acrylic, polyester, and olefin

6. Fibers Vary widely in class characteristics
Fibers are very useful as trace evidence:
Vary widely in class characteristics
color, shape, chemical composition, etc.
Easily transferred from one source to another (carpets, clothes, etc.)
Significant persistence (won’t degrade)

7. Importance of Fiber Evidence
Perpetrators of crimes are not always aware or able to control the fibers they have left behind or picked up

8. How are fibers used as evidence?
Trace > Fibers
How are fibers used as evidence?
As with other trace evidence, fibers can be transferred to/from a person or objects linking them to one another.

9. How long do fibers persist?
Trace > Fibers
How long do fibers persist?
Most fiber evidence is lost (fall off) a short time after the transfer occurs.
The fibers that do remain will be persistent.

10. Importance of Fiber Evidence
In contrast to hair, fibers offer much greater evidential value because they incorporate numerous variables
Number of fibers in each strand, diameter of strands and fibers, direction and number of twists, type of weave, and dye content, as well as foreign material embedded or adherent to the fiber

11. Introduction and How Forensic Scientists Use Fibers
Fiber Transfer
Direct Transfer
Secondary Transfer
Transfer occurs from victim to suspect or suspect to victim
Transfer occurs from a source to the victim then to the suspect
Give an example of this.
Forensic Science: Fundamentals & Investigations, Chapter 4

12. MiniActivity: Fiber Transfer
Procedures: Press the sleeves (or cuffs) or your clothing together. Examine your clothes for fiber transfer using masking tape and a hand lens.
Questions:
Can fibers from one sleeve be detected on the other?
Do masking tape and hand lenses aid the investigation? How?
Forensic Science: Fundamentals & Investigations, Chapter 4

13. Introduction and How Forensic Scientists Use Fibers
THINK: Why are dead bodies no longer shrouded (or covered) in cotton sheets? Why are plastic body bags used instead?
Forensic Science: Fundamentals & Investigations, Chapter 4

14. Introduction and How Forensic Scientists Use Fibers
In an investigation, collection of fibers within 24 hours is critical.
Why?
Fiber evaluation can show such things as the type of fiber, its color, the possibility of violence, location of suspects, and point of origin.
Forensic Science: Fundamentals & Investigations, Chapter 4

15. Introduction and How Forensic Scientists Use Fibers
Questions a forensic scientist will consider when examining fiber evidence:
What type of fiber is it?
What is the fibers color?
Number of fibers found?
Where was the fiber found?
Textile the fiber originated from?
Are there multiple fibers transferred?
What type of crime was committed?
Time between crime and discovery of fibers?
Forensic Science: Fundamentals & Investigations, Chapter 4

16. Sampling and Testing How are fibers collected? Special Vacuums
Sticky Tape
Forceps (tweezers)
Black Lights
Magnifying Glasses
Forensic Science: Fundamentals & Investigations, Chapter 4

17. Trace > Fibers > Analysis
Begin by identifying and comparing class characteristics for unknown sample (evidence) and known sample.
Known
Unknown

18. Fibers from rug in a van. Fibers found on victim.
Trace > Fibers > Analysis
Fibers from rug in a van.
Fibers found on victim.

19. Sampling and Testing
Weaving spun fibers (yarns) together produces clothing and many textiles.
Shedding from an article of clothing or a textile is the most common form of fiber transfer.
Natural fibers require only an ordinary microscope to find characteristic shapes and markings.
Infrared spectroscopy can reveal something of the chemical structure of other fibers that, otherwise, may look very much alike.
Forensic Science: Fundamentals & Investigations, Chapter 4

20. Sampling and Testing
If a large quantity of fibers is found, some can be subjected to destructive tests such as burning them in a flame (see analysis key above) or dissolving them in various liquids.
Crimes can be solved in this way by comparing fibers found on different suspects with those found at the crime scene.
Forensic Science: Fundamentals & Investigations, Chapter 4

21. Fibers can be classified into three main categories:
Trace > Fibers
Fibers can be classified into three main categories:
Natural (animal, plant, mineral)
Manufactured
Synthetic

22. Fiber Classification —Natural Fibers
woven wool textile
Animal fibers (made of proteins):
Wool from sheep, cashmere and mohair from goats, angora from rabbits, and hair from alpacas, llamas, and camels are commonly used in textiles.
Shimmering silk from caterpillar cocoons is longer and not as easily shed.
Forensic Science: Fundamentals & Investigations, Chapter 4

23. Fiber Classification —Natural Fibers
Plant fibers (made of the polymer cellulose):
can absorb water.
are insoluble in water.
are very resistant to damage from harsh chemicals.
can only be dissolved by strong acids.
can be common at crime scenes because they become brittle over time.
Forensic Science: Fundamentals & Investigations, Chapter 4

24. Fiber Classification —Natural Fibers
Plant fibers:
Cotton from seedpods is the plant fiber most commonly used in textiles (shown above).
Coir from coconuts is durable.
Hemp, jute, and flax from stems grow in bundles.
Manila and sisal from leaves deteriorate more quickly.
Mineral Fibers:
Fiberglass is a fibrous form of glass.
Asbestos is a naturally occurring mineral with a crystalline structure.
Forensic Science: Fundamentals & Investigations, Chapter 4

25. Fiber Classification —Synthetic (artificially produced) Fibers
Until the nineteenth century only plant and animal fibers were used to make clothes and textiles.
Half the products produced today are artificially produced.
Artificially produced fibers include rayon, acetate, nylon, acrylics, and polyesters.
Forensic Science: Fundamentals & Investigations, Chapter 4

26. Natural Fibers: Found in nature Can be artificially colored or treated
Trace > Fibers > Natural
Natural Fibers:
Found in nature
Can be artificially colored or treated
Cotton
Wool
Hemp

27. Animal Fibers Wool - Hairs from sheep Silk - comes from silkworm
Most common of animal fibers
Hairs are spun to form thread
Silk - comes from silkworm
Spun as double filament (separated before use)
Because of length, doesn’t shed easily
Other Hairs from Animals

28. Animal Fibers
Woolen fibers occupy less than 1% of all fibers used in production of textile materials
Wool has a microscopic structure that is characteristic of hair
The cuticle (outer covering) is made of flattened cells, commonly called scales

29. Animal Fibers (continued)
The scales resemble shingles of a roof and are one of the most useful features to ID an unknown textile fiber as wool
Other animal hairs are not as frequently encountered so they can be quite valuable if they occur as evidence
Include goat (cashmere, mohair), llama (alpaca, vicuna, guanaco), and camel hair

30. Animal Fibers
Cattle and rabbit hair are found in the manufacture of certain kinds of felts
Felts are made from water suspensions of randomly arranged fibers. When the fibers settle out, the water is removed and the mass of fibers is pressed to form the felt
Some modern felts are no longer made exclusively from hairs but are mixtures with other fibers

31. Animal Fibers
Silk places a distant second to wool in occurrence, and its use has decreased since development of artificial fibers
Silk fibers are not very often encountered in crime investigations, probably because silk fabrics do not shed very easily

32. Fiber and Textile Evidence
The most common fiber transfer is shedding of textiles (clothing, carpets, upholstery)
Fibers can be classified as:
Natural Fibers (come from animals, plants, and minerals minded from the ground)
Synthetic Fibers (are man mad and are either regenerated or polymers)
Forensic Science: Fundamentals & Investigations, Chapter 4

33. Plant Fibers Cotton - seed hairs of cotton plant
Trace > Fibers > Natural
Plant Fibers
Cotton - seed hairs of cotton plant
by far most common fiber (find almost everywhere)
Under microscope, fibers resemble twisted ribbon

34. Vegetable Fibers
Only cotton is found in any large extent in items of clothing
Approximately 24% of total US textile fiber production was cotton in 1979
Other plant fibers, such as jute and sisal, are seen in various types of cordage and baggings

35. Vegetable Fibers
Cotton fibers have a distinctive flattened, twisted microscopic appearance, which is quite characteristic
The fibers resemble a twisted ribbon
In mercerizing process, fibers are treated with alkali, making them swell up and become more rounded and less twisted in appearance.
This process results in improved texture and feel, but the fibers are still recognizable as cotton under the microscope

36. Vegetable Fibers
Undyed cotton fibers are so common they have little value as physical evidence
Almost any surface or dust sample will be found to contain white cotton fibers
Household Dust

37. Other Plant Fibers: Linen - stem fiber from flax plant
Trace > Fibers > Natural
Other Plant Fibers:
Linen - stem fiber from flax plant
Kapok - from seed hairs of kapok plant
Other fibers - Manila, hemp, sisal, jute

38. Mineral Fibers Asbestos - crystalline material
Used to be used for insulation
Fractures into thin rods that can get into your lungs; can kill you
Not used much anymore

39. Filament vs. Staple Filament: Long continuous fiber (like silk)
Staple: Filament is cut into smaller pieces; staples are spun together to form thread (like cotton)

40. Manade Fibers
Represent approximately 75% of total textile fiber production in US
Can be defined as a fiber of a particular chemical composition that has been manufactured into a particular shape and size, contains a certain amount of various additives, and has been processed in a particular way

41. Manmade Fibers
Within the 6 most seen of the 21 generic classifications established by the US Federal Trade Commission, there are well over a 1,000 different fiber types
Therefore, numerous fiber types can be present in the composition of textile materials
This is true before even considering differences in color

42. Fiber Classification —Synthetic (artificially produced) Fibers
Regenerated Fibers (derived from cellulose):
Rayon is the most common of this type of fiber. It can imitate natural fibers, but it is stronger.
Celenese® is cellulose chemically combined with acetate and is often found in carpets.
Polyamide nylon is cellulose combined with three acetate units, is breathable, lightweight, and used in performance clothing.
Forensic Science: Fundamentals & Investigations, Chapter 4

43. Manufactured Fibers Regenerated Fibers Example: Rayon
Cellulose is dissolved, then resolidified to form the polymer fiber
Can occur in filament or staple form
Example: Rayon

44. Synthetic Fibers Man made Can also be filament or staple Examples:
Nylon and Polyester

45. Synthetic Fibers Acrylics More common as evidence
Usually in staple form
Staples spun together, similar to wool

46. Class characteristics
Trace > Fibers > Analysis
Class characteristics
Color: microscopic examination
Size: length and width can be measured
Shape: cross section is viewed

47. Class characteristics
Refractive Index – n. The ratio of the speed of light in air or in a vacuum to the speed of light in another medium.
Other microscopic properties (PLM)

48. Class characteristics
Chemical Composition: determined by advanced instrumentation

49. Fiber Classification —Synthetic (artificially produced) Fibers
Synthetic Polymer Fibers:
Petroleum is the basis for these fibers, and they have very different characteristics from other fibers.
Monomers in large vats are joined together to form polymers. The fibers produced are spun together into yarns.
They have no internal structures, and under magnification they show regular diameters.
Forensic Science: Fundamentals & Investigations, Chapter 4

50. Fiber Classification—Synthetic (artificially produced) Fibers
spandex nylon
Examples of synthetic polymer fibers:
Polyester—found in “polar fleece,” wrinkle-resistant, and not easily broken down by light or concentrated acid; added to natural fibers for strength.
Nylon—easily broken down by light and concentrated acid; otherwise similar to polyester.
Acrylic—inexpensive, tends to “ball” easily, and used as an artificial wool or fur.
Olefins—high performance, quick drying, and resistant to wear.
Forensic Science: Fundamentals & Investigations, Chapter 4

51. Comparison of Natural and Synthetic Fibers
Visual Diagnostics of Some Common Textile Fibers
under Magnification
Forensic Science: Fundamentals & Investigations, Chapter 4

52. Yarns, Fabrics, and Textiles
Fibers can be twisted (spun) into yarn of any length, thick or thin, loose, or tight. A blend can be made to meet different needs such as resistance to wrinkling.
Fibers can be woven into fabrics or textiles.
Threads are arranged side by side (the warp).
More threads (the weft) then are woven back and forth crosswise in one of a number of different patterns through the warp.
Forensic Science: Fundamentals & Investigations, Chapter 4

53. Threads, Yarn, Rope, Cordage
Smallest component is fibers (staple) twisted together to form thread or is a filament.
This thread can then be twisted with other threads to form a thicker thread (string, etc.)
This thicker cord can then be twisted with other thicker cords, etc.

54. Threads, Yarn, Rope, Cordage
Small cords or fibers twisted together to form larger cords
At each step, the number of cords can be counted.
At each step, the twist direction is either “S” or “Z”

55. Yarns, Fabrics, and Textiles
Warp: lengthwise threads
Weft: crosswise threads
Weave Pattern: The pattern in which the weft passes over and under the warp.
Forensic Science: Fundamentals & Investigations, Chapter 4

56. Forensic Science: Fundamentals & Investigations, Chapter 4

57. Yarns, Fabrics, and Textiles
Weave Patterns
Forensic Science: Fundamentals & Investigations, Chapter 4

58. Important to Remember:
It is important to collect evidence from both complainants and suspects as soon as possible
Studies show that some 80% of fibers can be expected to be lost in four hours, with just 5-10% remaining at the end of 24 hours

59. Methods of Examination
In the recent past, the ID and comparison of fibers were at a relatively simple level which relied heavily on microscopy

60. From Less than 1 cm of a 20 mm Diameter Fiber It is Possible to Determine:
Generic class
Polymer composition
Finish--bright/dull
Cross-sectional shape
Melting point
Refractive Indices
Birefringence
Color
Fluorescence
Absorption spectrum
Dye class
Dye Components

61. Microscopy
Microscopic examination provides the quickest, most accurate, and least destructive means of determining the microscopic characteristics and polymer type of textile fibers.

62. Microscopic View
Acetate Dacron

63. Stereomicroscope Should be used first to examine fibers.
Physical features such as crimp, length, color, relative diameter, luster, apparent cross section, damage, and adhering debris should be noted.
Fibers are then tentatively classified into broad groups such as synthetic, natural, or inorganic.

64. Comparison Microscope
If all of the characteristics are the same under the stereoscope, then the comparison microscope is used.
A point-by-point and side-by-side comparison provides the most discriminating method of determining if two or more fibers are consistent with originating from the same source.

65. Scenario Discussions
Working with a different group for each question discuss and then record your reasoning for each.
What if a woman’s roommate borrowed her coat and was then involved in a crime that left textile evidence behind?
How could investigators distinguish between the woman involved in the crime and the owner of the coat?
Would you ever be 100% sure of the conclusion you made? Explain
Forensic Science: Fundamentals & Investigations, Chapter 4