Forensic Fiber Analysis Overview

Questions and Answers

The most common type of regenerated fiber, which is derived from cellulose and is mostly plant in origin, is rayon.

True

Synthetic polymer fibers, which all originate with petroleum products, are cellulose-based fibers.

False

Polyester has properties similar to nylon except it is easily broken down by light and concentrated acid.

False

A disadvantage of manufactured fibers is that they can deteriorate in bright sunlight and melt at a lower temperature than natural fibers.

True Signup and view all the answers

Fibers are woven into textiles or fabrics.

True Signup and view all the answers

Fibers that have been spun together are called:

Yarn Signup and view all the answers

A small molecule that may bond to other monomers to become a polymer is a:

Monomer Signup and view all the answers

When fibers are transferred directly from victim to suspect or suspect to victim, this is called:

Direct transfer Signup and view all the answers

The transfer of evidence such as a fiber from a source to a person, then to another person, is called:

Secondary transfer Signup and view all the answers

Early collection of fibers in an investigation is critical. Within 24 hours, an estimated:

95% of the fibers are lost Signup and view all the answers

A forensic scientist will ask questions about:

Type of fiber, fiber color, number of fibers found, where the fiber was found, textile from which fiber originated Signup and view all the answers

Fiber evidence is gathered with:

Vacuums, Tape, Forceps, Glue, Lint roller Signup and view all the answers

Fibers are classified as either:

Natural or synthetic fibers Signup and view all the answers

Natural fibers come from:

Animals, plants, minerals that are mined from the ground Signup and view all the answers

Natural plant fibers are produced from:

Seeds, fruits, stems, and leaves Signup and view all the answers

All plant fibers share the common polymer that is:

Cellulose Signup and view all the answers

One seed fiber is:

Cotton Signup and view all the answers

Fiberglass is a form of:

Glass Signup and view all the answers

Until the nineteenth century, only plant or animal fibers were used to make clothing and textiles. Half the fibers produced today are synthetic. They are categorized as:

Regenerated fibers and polymers Signup and view all the answers

Weave patterns have names like:

Tabby, twill and satin Signup and view all the answers

The simplest weave is the plain weave or:

Tabby weave Signup and view all the answers

The number of threads that are packed together for any given amount of fabric is known as the:

Thread count Signup and view all the answers

Manila is a fiber extracted from the leaves of ______, a relative of the banana tree.

Abaca Signup and view all the answers

Flax is the most common stem fiber, and is most commonly found in the textile,

Linen Signup and view all the answers

What are things that determine transfer of fibers?

Duration of contact, type of contact, type of fiber Signup and view all the answers

When collecting fibers, which ones are you most likely to collect and why?

Fibers you would not expect to be found would be examined because they most likely were not there before. Signup and view all the answers

Once collected, how are fibers analyzed in the lab?

First task is to identify the fiber, shape, and color and do chemical tests. If there are only few fibers collected, chemical tests will not be done. Signup and view all the answers

What four methods were discussed as ways that forensic scientists can complete fiber analysis without damaging the fibers? Discuss what each of these methods allows scientists to see.

-Polarizing light microscopy: uses a microscope with a special filter that allows the scientist to look at the fiber using specific light wavelengths. -Infrared spectroscopy: emits a beam that bounces off the material and returns to the instrument. -When shining an ultraviolet light on fibers, the light can be re-emitted at a lower, more visible wavelength. -Microspectrophotometry: the measure of the spectra of microscopic samples using different wavelengths of electromagnetic radiation. Signup and view all the answers

How is the value of fiber evidence determined at a crime scene?

Evidence must be evaluated since the fibers are so abundant; fibers are evaluated by how unique they are to the crime scene. Signup and view all the answers

What is the most common form of fiber transfer that is encountered at a crime scene?

Fibers shed from a textile Signup and view all the answers

How are textiles formed?

Woven or knitted together Signup and view all the answers

Where do natural fibers come from?

Plants, animals, minerals Signup and view all the answers

How do you tell the difference between natural and synthetic fibers?

Natural fibers come from animals, plants, and minerals that are mined from the ground. Synthetic fibers are categorized as regenerated fibers and polymers. Signup and view all the answers

How can you tell the difference between plant fibers and animal fibers?

Plant fibers are specialized by plant cells. They come from seeds, fruits, stems, and leaves. Animal fibers come from three sources: hair, fur, and webbing. All animal fibers are made of proteins. Signup and view all the answers

What are some common forms of seed fibers? Where are they used?

Cotton is found in the seedpod of the cotton plant. Cotton can be woven and dyed easily. Signup and view all the answers

Where are leaf fibers used?

Manila is a fiber extracted from the leaves of abaca; this can be used to make ropes, twines, and netting. It is commonly seen as green garden twine or on farms as the twine on hay bales. Signup and view all the answers

What are mineral fibers? Give an example of mineral fibers.

Mineral fibers are neither proteins nor cellulose. Fiberglass is a fiber form of glass. Rolls of fiberglass batting are used to insulate buildings. Asbestos is a mineral naturally occurring in different types of rocks. Signup and view all the answers

What are synthetic fibers? Give some examples.

Regenerated fibers and polymers. They are manufactured fibers include rayon, acetate, nylon, acrylics, and polyesters. Signup and view all the answers

How are regenerated fibers made?

Regenerated fibers are derived from cellulose and are mostly plant in origin. The most common of this type is rayon. It is a fiber that can imitate natural fibers and generally is smooth and silky in appearance. Cellulose chemically combined with acetate produces the fiber Celanese® that is used in carpets. When cellulose is combined with three acetate units, it forms polyamide nylon (such as Capron®)—a breathable, lightweight material used in high-performance clothing. Signup and view all the answers

Compare the strength and durability of synthetic and natural fibers.

Synthetic fibers are stronger than the strongest natural fibers. Unlike natural fibers, manufactured fibers are not damaged by microorganisms. A disadvantage of manufactured fibers is that they can deteriorate in bright sunlight and melt at a lower temperature than natural fibers. Signup and view all the answers

What is yarn? How is it made?

Fibers too short in their natural state to be used to make textiles may be spun together to make yarns. (Very thin yarns are often called threads.) Short cotton fibers only two centimeters long can be twisted into very strong yarn of any length. Rope is simply a very thick yarn. Depending on their use, yarns may be spun thick or thin, loose or tight. Some may be a blend of fibers, such as wool and polyester, to give desired qualities such as strength or wrinkle resistance. Any given yarn will have a direction of twist. Signup and view all the answers

What is the warp?

A lengthwise yarn or thread in a weave Signup and view all the answers

What is a weft?

A crosswise yarn or thread in a weave Signup and view all the answers

Describe the weaving of textiles... How are they woven?

Weaving originated with basket-making. Stone Age humans used flax fibers to weave linen cloth. Fibers are woven into textiles in their natural state, if they are long enough, or once they are spun into yarns. Weaving machines were introduced in the early 1700s. Today, enormous industrial looms weave most textiles. Signup and view all the answers

What are other examples of weave patterns?

Plain, Basket, Leno, Twill, Satin Signup and view all the answers

What three ways do fibers differ?

Weave pattern, thread count, two ply Signup and view all the answers

What does thread count refer to?

Thread count is the number of horizontal and vertical threads in a square inch of fabric. Signup and view all the answers

What does two-ply refer to?

If the weave is two threads twisted together. Signup and view all the answers

Why can fibers not be used to convict someone?

True Signup and view all the answers

A fiber is collected at a crime scene. When viewed under a compound microscope, what traits would indicate that the fiber was a human hair and not a piece of fiber obtained from an article of clothing?

If the article has a follicle, medula, cortex, it will indicate if it is obtained from an article of clothing. Signup and view all the answers

Describe asbestos as a fiber. What is its use? Why do people who work in construction and contracting have to be cautious about it?

Asbestos is very durable. Its many uses once included pipe coverings, brake linings, ceiling tiles, floor tiles, shingles, home siding, and insulation for building materials. Due to its health risks, it is no longer commonly used. Signup and view all the answers

What is coir?

Coconut fibers Signup and view all the answers

What common protein do all plant fibers have in common?

Cellulose Signup and view all the answers

Study Notes

Fibers Overview

Rayon is the most common regenerated fiber, derived from cellulose, primarily from plants.
Synthetic fibers originate from petroleum products, not cellulose-based fibers.
Polyester shares similarities with nylon but is not easily broken down by light and concentrated acids, contrary to some beliefs.

Properties of Manufactured Fibers

Manufactured fibers can deteriorate under bright sunlight and melt at lower temperatures compared to natural fibers.
Fibers are formed into textiles or fabrics through processes like weaving and knitting.

Fiber Evidence in Forensics

Fibers spun together form yarn, which can be found in various textiles.
Direct transfer occurs when fibers move directly from one person to another; secondary transfer involves an intermediate person.
Rapid collection of fibers is crucial as 95% can be lost within 24 hours of a crime.