Fabrics are composed of individual threads or yarns made of fibers Fabrics are composed of individual threads or yarns made of fibers Fibers are knitted, woven, bonded, crocheted, felted, or knotted together Fibers are knitted, woven, bonded, crocheted, felted, or knotted together Most are either woven or knitted Most are either woven or knitted Individual qualities of fabrics include: Individual qualities of fabrics include: Degree of stretch Degree of stretch Absorbency Absorbency Water repellence Water repellence Softness Softness Durability Durability

Yarn Yarn Continuous strand of fibers or filaments that may be twisted together Continuous strand of fibers or filaments that may be twisted together Warp Warp Lengthwise yarn in fabric Lengthwise yarn in fabric Weft Weft Crosswise yarn in fabric Crosswise yarn in fabric Blend Blend Fabric made up of two or more different types of fibers Fabric made up of two or more different types of fibers

Plain Plain Simplest & most common pattern Simplest & most common pattern Warp & weft yarns pass under each other alternately Warp & weft yarns pass under each other alternately Design resembles a checkerboard Design resembles a checkerboard Satin Satin Yarn interlacing isn’t uniform Yarn interlacing isn’t uniform Interlacing weave passes over four or more yarns Interlacing weave passes over four or more yarns Creates long floats Creates long floats Twill Twill Warp yarn is passed over one to three weft yarns before going under one. Warp yarn is passed over one to three weft yarns before going under one. Makes diagonal weave pattern Makes diagonal weave pattern Denim is most common example Denim is most common example

Knitted fabrics are made by interlocking loops into a specific arrangement Knitted fabrics are made by interlocking loops into a specific arrangement May be one continuous thread or a combination May be one continuous thread or a combination Yarn is formed into successive rows of loops & then drawn through another series of loops to make the fabric Yarn is formed into successive rows of loops & then drawn through another series of loops to make the fabric

All fabrics are long chains of monomers called polymers All fabrics are long chains of monomers called polymers Limited number of natural fibers but 1000s of artificial fibers Limited number of natural fibers but 1000s of artificial fibers Polymer properties vary Polymer properties vary Chemical structure of monomers vary Chemical structure of monomers vary Chemical bond of monomers vary Chemical bond of monomers vary Because of these differences, polymers can be distinguished form one another forensically Because of these differences, polymers can be distinguished form one another forensically

Characteristics that can be used to identify & compare fibers as forensic evidence: Characteristics that can be used to identify & compare fibers as forensic evidence: Fiber cross section Fiber cross section Chemical structure Chemical structure Microscopic observation Microscopic observation Burn tests Burn tests Thermal decomposition Thermal decomposition Chemical tests Chemical tests Density Density Refractive index Refractive index Fluorescence Fluorescence

Synthetic fibers are forced out of a nozzle when they are hot & then woven Synthetic fibers are forced out of a nozzle when they are hot & then woven Holes of the nozzle are not always round so fiber filament may have a unique shape in the cross section Holes of the nozzle are not always round so fiber filament may have a unique shape in the cross section

Microscopic observation Microscopic observation Compare color, diameter, twist, number of strands, etc Compare color, diameter, twist, number of strands, etc Thermal Decomposition Thermal Decomposition Use heat to break down the fiber to basic monomers Use heat to break down the fiber to basic monomers Example: acetate fibers decompose to form acetic acid Example: acetate fibers decompose to form acetic acid Burn Tests – how fibers burn Burn Tests – how fibers burn Odor Odor Color of flame Color of flame Color of smoke Color of smoke Appearance of residue Appearance of residue

Chemical Tests Chemical Tests Solubility & decomposition Solubility & decomposition Separates waft & weft Separates waft & weft Density Density Mass of an object divided by its volume Mass of an object divided by its volume Especially useful for single fibers Especially useful for single fibers Nondestructive to fibers Nondestructive to fibers

Refractive index Refractive index Measurement of the bending of light as it passes from air into a solid or liquid Measurement of the bending of light as it passes from air into a solid or liquid Becke line is halo-like shadow appearing around an object immersed in a liquid of different refractive index Becke line is halo-like shadow appearing around an object immersed in a liquid of different refractive index If liquid & fiber have same refractive value, fiber becomes invisible because it bends light at the same angle as liquid If liquid & fiber have same refractive value, fiber becomes invisible because it bends light at the same angle as liquid If liquid has lower or higher refractive value, the fiber can be seen If liquid has lower or higher refractive value, the fiber can be seen Fiber has “halo” of a dark boundary Fiber has “halo” of a dark boundary Becke line outside fiber edges means liquid has higher refractive index than fiber Becke line inside fiber image means liquid has lower refractive index than fiber

Fluorescence Fluorescence Absorption & reemission of light when exposed to UV radiation Absorption & reemission of light when exposed to UV radiation Expose to both long & short wave radiation for comparison Expose to both long & short wave radiation for comparison May be caused by chemical properties of fabric itself or dyes/optical brighteners added to fabric May be caused by chemical properties of fabric itself or dyes/optical brighteners added to fabric Used for comparing fibers as well as spotting fibers for collection Used for comparing fibers as well as spotting fibers for collection

Component of dyes can be separated & matched to unknown Component of dyes can be separated & matched to unknown More than 7,000 different dye formulations More than 7,000 different dye formulations Chromatography is used to separate dyes for comparative analysis Chromatography is used to separate dyes for comparative analysis The way a fabric accepts a particular dye can be used to identify & compare samples The way a fabric accepts a particular dye can be used to identify & compare samples

Put clothing items individually in paper bags Put clothing items individually in paper bags Make sure that different items are not placed on the same surface before being bagged. Make sure that different items are not placed on the same surface before being bagged. Make tape lifts of exposed skin areas & any inanimate objects Make tape lifts of exposed skin areas & any inanimate objects Removed fibers should be folded into a small sheet of paper & stored in a paper bag Removed fibers should be folded into a small sheet of paper & stored in a paper bag

Fiber evidence in court cases can be used to connect the suspect to the victim or to the crime scene 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 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, in his car, & on several murder victims Williams was convicted in 1982 based on carpet fibers that were found in his home, in his car, & on several murder victims