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.

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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

What is important What is important about fibers found at a about fibers found at a

crime scene?crime scene? Type Type ColorColor ShapeShape # of fibers found# of fibers found Textile it originated from (carpet/curtains)Textile it originated from (carpet/curtains) Multiple fiber transferMultiple fiber transfer Type of crime being investigatedType of crime being investigated Time between crime and discovery of fiberTime between crime and discovery of fiber 3

Collected by:Collected by: Sticky tapeSticky tape ForcepsForceps Special vacuumsSpecial vacuums

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Analyze fibers by Analyze fibers by using:using:

Infrared spectroscopy – bounces beam offInfrared spectroscopy – bounces beam off

If multiple fibers are available-If multiple fibers are available- Burn testsBurn tests Dissolving test (chemicals)Dissolving test (chemicals) 5

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Fabric Fibers are made of twisted filaments

2 types:

AnimalAnimal PlantPlant MineralMineral

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man-mademan-madesynthesized or created from altered natural sources

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Natural

Silk Cotton Wool Mohair Cashmere Angora

Natural FibersNatural Fibers

AnimalAnimal Made of protein (Hair and silk)Made of protein (Hair and silk)

PlantPlant Made of celluloseMade of cellulose

From seeds, fruit, stems, and leavesFrom seeds, fruit, stems, and leaves

MineralsMinerals Not made from protein or celluloseNot made from protein or cellulose

Fiberglass and asbestosFiberglass and asbestos

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Cellulose Fibers

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.

Where does cellulose come from?

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Fiber Comparison

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

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Protein Fibers

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

Where does the protein come from?

Spider Silk

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Mineral Fibers

Asbestos—a natural fiber that has been used in fire-resistant substances

Rock wool—a manufactured mineral fiber (insulation)

Fiberglass—a manufactured inorganic fiber

Where do minerals come from?

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Synthetic

Rayon Nylon Acetate

(taffeta) Acrylic Spandex Polyester

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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

About About halfhalf of the fibers are synthetic of the fibers are synthetic

Two typesTwo types

1. 1. Regenerated fibersRegenerated fibers Modified natural fibers Modified natural fibers

Example – rayonExample – rayon

2. 2. PolymersPolymers Made from petroleum productsMade from petroleum products No definite shape or sizeNo definite shape or size

Examples – acetate, nylon, acrylics, polyestersExamples – acetate, nylon, acrylics, polyesters

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YarnYarn

Fibers can made into Fibers can made into yarnyarn – twisted – twisted around each other – can analyze twisting around each other – can analyze twisting pattern.pattern.

YarnYarn is then is then weavedweaved into into TextilesTextiles (material/cloth)(material/cloth) It is weaved into different patterns that can It is weaved into different patterns that can

be used for identification.be used for identification.

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Weave Terminology

Warp—lengthwise yarn (attached to beam)

Weft—crosswise yarn

Blend—a fabric made up of two or more different types of fiber.

http://www.youtube.com/watch?v=Q0i5VMNfuew

http://www.youtube.com/watch?v=cqjhvOuKLR8&feature=&p=375E2F151778D5D8&index=0&playnext=1

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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

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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

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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

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Weave Patterns

Plain

Satin

Twill

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Weave Patterns

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Knitted FabricInterlocking loops into a

specific arrangement.

It may be one continuous thread or a combination.

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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.

Testing for Identification Microscopic observation

- Color--compositional differences in Color--compositional differences in the dyesthe dyes

- Fibers surface--delustering - Fibers surface--delustering particles that may particles that may be added by be added by manufacturersmanufacturers

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

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.

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What is the function of fiber evidence?

With trace evidence, an investigator usually With trace evidence, an investigator usually cannotcannot say that one say that one piece of evidence definitely originated from a specific item.piece of evidence definitely originated from a specific item.

The investigator can only tell the jury what similarities were found The investigator can only tell the jury what similarities were found and give them an idea of how rare those similarities are.and give them an idea of how rare those similarities are.

The Forensic Scientist’s main objective is to give the jury an idea The Forensic Scientist’s main objective is to give the jury an idea about about how rare the category ishow rare the category is..

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Fiber EvidenceFiber 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 Although this case is unusual, fibers are generally considered of greater value as generally considered of greater value as evidence than that of rootless hairs since evidence than that of rootless hairs since they may contain a greater number of they may contain a greater number of variables, thus showing more individual variables, thus showing more individual characteristicscharacteristics..

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

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Pollen SamplesPollen Samples

Are unique to each speciesAre unique to each speciesVary in appearance, size and colorVary in appearance, size and colorCan last unchanged for extended Can last unchanged for extended

periods of timeperiods of time

Match suspect with Match suspect with crime scenecrime scene

Any residue found to be a matchon clothing, shoes, or personcould place suspect at the scene

Flower

Pine tree

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All pollen is uniqueAll pollen is unique

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You can identify the You can identify the type of planttype of plant

and maybe its and maybe its location by its location by its

pollenpollen

Magdeberg, Germany CaseMagdeberg, Germany CaseLondon,London, Reuters 30 Sept. 1998Reuters 30 Sept. 1998

32 skeletons discovered in a mass grave in eastern 32 skeletons discovered in a mass grave in eastern Germany were either killed by the Gestapo in the Germany were either killed by the Gestapo in the spring of 1945 or by Russian secret police putting spring of 1945 or by Russian secret police putting down a German revolt in the summer of 1953down a German revolt in the summer of 1953

Pollen evidence showed summer blooming oak, Pollen evidence showed summer blooming oak, plantain, and grasses indicating that the bodies were plantain, and grasses indicating that the bodies were Russian troops that were executed by the Russian Russian troops that were executed by the Russian secret police for refusing to fire on German civilians secret police for refusing to fire on German civilians

http://discovermagazine.com/1999/feb/offlowersandmurd1587

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Beach and River SandsBeach and River Sands

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X-Ray DiffractometerX-Ray DiffractometerFor Mineral IdentificationFor Mineral Identification

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More about Fibers

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

www.crimelibrary.com/criminal_mind/forensics/trace/1.html

http://www.bbc.co.uk/news/uk-16257377