FIBERS 1 Fiber is the smallest unit of

FIBERS 1. Fiber: is the smallest unit of a textile material woven or twisted together to form a thread or yarn. 2. Fiber evidence in court cases can be used to connect the suspect to the victim or to the crime scene. 3. Are considered class evidence 4. Have probative value- can create connection btwn a victim and suspect

OBJETIVES: 1. Introduction (How do fibers have probative value? ) � 2. Forensic significance(Why are fibers valuable at a crime scene? ) � 3. Fiber and types of fabrics � 4. Fiber production(How are fabrics made? ) � 5. What are the different characteristics of a fiber, a filament & a fabric? � 6. Collection � 7. Examination � 8. Problems with fiber Evidence �

WHAT IS THE SIGNIFICANCE OF FIBER EVIDENCE? 1. 2. 3. Can prove contact between two individuals Can prove contact between an individual and an object. Value is dependent on: �Type of fiber �Color or color variations in fiber �Location of fiber �Number of fibers that matches between victim and suspect.

FIBER AS TRACE EVIDENCE Primary transfer occurs when fibers are transferred from a fabric directly onto a victim's clothing. Secondary transfer occurs when already transferred fibers on the clothing of a suspect transfers to clothing of a victim. • Important for reconstruction of crime scene.

USING FIBERS TO RECONSTRUCT CRIME SCENES 1. 2. 3. 4. The condition of the garment/fiber The type and composition of the fabric. Mobility of victim • The more movement, the more likely fibers will be transferred The length of time between actual physical contact. • Likelihood of finding transferred fibers on the clothing of the suspect decreases after each day that passes.

FABRIC 1. Fabric is made of fibers. 2. Fibers are made of twisted filaments. 3. Types of fibers and fabric: - Natural—animal, vegetable, or inorganic - Artificial—synthesized or created from altered natural sources

TYPES OF FIBERS Synthetic Rayon Nylon Acetate Acrylic Spandex Polyester Natural Silk Cotton Wool Mohair Cashmere

CLASSIFICATION Natural fibers are classified according to their origin: 1. Vegetable or cellulose 2. Animal or protein 3. Mineral

CELLULOSE FIBERS 1. Cotton—vegetable fiber; strong, tough, flexible, moisture-absorbent, not shape-retentive 2. Rayon—chemically altered cellulose; soft, lustrous, versatile 3. Cellulose acetate—cellulose that is chemically altered to create an entirely new compound not found in nature

FIBER COMPARISON Describe the difference(s) between the cotton on the left and the rayon on the right.

PROTEIN FIBERS 1. Wool—animal fiber coming most often from sheep, but may be goat (mohair), rabbit (angora), camel, alpaca, llama, or vicuña 2. Silk—insect fiber that is spun by a silkworm to make its cocoon; the fiber reflects light and has insulating properties

MINERAL FIBERS 1. Asbestos—a natural fiber that has been used in fireresistant substances 2. Rock wool—a manufactured mineral fiber 3. Fiberglass—a manufactured inorganic fiber

SYNTHETIC FIBERS Made from derivatives of petroleum, coal, and natural gas. 1. Nylon—most durable of man -made fibers; extremely lightweight 2. Polyester—most widely used man-made fiber 3. Acrylic—provides warmth from a lightweight, soft, and resilient fiber 4. Spandex—extreme elastic properties

MAN-MADE FIBERS Fibers derived from either natural or synthetic polymers �Regenerated Fibers �Synthetic Fibers

FABRIC PRODUCTION 1. 2. 3. Fabrics are composed of individual threads or yarns that are made of fibers and 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.

WEAVE TERMINOLOGY 1. Yarn—a continuous strand of fibers or filaments that may be twisted together 2. Warp—lengthwise yarn 3. Weft—crosswise yarn 4. Blend—a fabric made up of two or more different types of fibers

WEAVE PATTERNS

PLAIN WEAVE 1. The simplest and most common weave pattern 2. The warp and weft yarns pass under each other alternately 3. Design resembles a checkerboard

TWILL WEAVE 1. The warp yarn is passed over one to three weft yarns before going under one. 2. Makes a diagonal weave pattern. 3. Design resembles stair steps. 4. Denim is one of the most common examples.

SATIN WEAVE 1. The yarn interlacing is not uniform 2. Creates long floats 3. Interlacing weave passes over four or more yarns 4. Satin is the most obvious example

KNITTED FABRIC 1. Knitted fabrics are made by interlocking loops into a specific arrangement. 2. It may be one continuous thread or a combination. 3. The yarn is formed into successive rows of loops and then drawn through another series of loops to make the fabric.

POLYMERS 1. Synthetic fibers are made of polymers, which are long chains of repeating chemical units. 2. The word polymer means many (poly) units (mer). 3. The repeating units of a polymer are called monomers. 4. By varying the chemical structure of the monomers or by varying the way they are joined together, polymers are created that have different properties. 5. As a result of these differences, they can be distinguished from one another forensically.

FILAMENT CROSS SECTIONS 1. 2. 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. Round 4 -lobed Octalobal Trilobal Irregular Dogbone or Dumbbell Multi-lobed or Serrate

COLLECTION OF FIBER EVIDENCE 1. Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged. 2. Make tape lifts of exposed skin areas and any inanimate objects. 3. Removed fibers should be folded into a small sheet of paper and stored in a paper bag.

TESTING FOR IDENTIFICATION 1. Microscopic observation 2. Burning — observation of how a fiber burns, the odor, color of flame, color of smoke, and the appearance of the residue 3. Thermal decomposition — gently heating to break down the fiber to the basic monomers 4. Chemical tests — solubility and decomposition

5. Density — the mass of an object divided by the volume of the object 6. Refractive index — measurement of the bending of light as it passes from air into a solid or liquid 7. Fluorescence — absorption and reemission of light; used for comparing fibers as well as spotting fibers for collection

DYES 1. Components that make up dyes can be separated and matched to an unknown. 2. There are more than 7, 000 different dye formulations. 3. Chromatography is used to separate dyes for comparative analysis. 4. The way a fabric accepts a particular dye may also be used to identify and compare samples

8) Chromatography: separation of dyes by thin layer chromatography (TLC) Rf value = distance of pigment distance of solvent front

OTHER TEST USED IN FIBER ANALYSIS 9) FTIR: Fourier Transform Infrared • based on the absorption and wavelength of light in a fabrics polymer. • can be used on a single fiber • Non-destructive 10) PGS-MS: Pyrolysis Gas Chamber-Mass Spectrometry � � � Burns and separates each combustion product of sample Match results of chromatogram & products to known Can be used in short length fibers but is destructive.

FIBER FORENSICS FYI- do not copy � analyst gets only a limited number of fibers to work with—sometimes only one. � Fibers are sent to the lab for analysis. � Fibers from scene are compared to victim Copy### � Any inconsistency (one property does not match) is sufficient to cancel association

FIBER TRANSFER AND PERSISTENCE Fibers can be used as trace evidence due to fiber transfer. � How easy the fiber is transferred is affected by: � � � � Area of contact the amount of pressure used Any friction due to side contact Number of passes or contacts Kind of clothing donor/recipient was wearing Fiber type, length and texture History of the garment.

� How long transfer fibers remain on victim is fiber persistence. � Time of wear and movement � What is covering the fabric � Type of activity � Weather condition ** fiber persistence decreases exponentially with time of wear.

TYPES OF FIBERS - KEY A Acrylic Yarn Polyester Yarn B D Cotton Yarn Rayon Rope C E Nylon Rope Wool Yarn F

PROBLEMS WITH FIBER EVIDENCE 1. Class Characteristic • 2. Mass production of goods/garments The less common the fiber the more useful it is to identify a suspect. • Cotton: Very common – Basically meaningless in forensic investigations.