Fibers Notes on Page 24-25

What information can fibers give us? Type of fiber Color of fiber Number of fibers Where was the fiber found? Textile of fabric (upholstery from car, carpet fibers?) Multiple fiber transfers Time between crime and discovery of fiber Type of fiber – what is the composition of the fiber? Is it common or rare? What suspects, victims or part of the crime scene had this type of fiber on them? Number of fibers could suggest more violence or longer period of contact Location of fiber could tell investigators how close the suspect was to the crime scene, to the victim

How are fibers left or picked up at a crime scene? Direct transfer – fibers originating from carpets, clothing, linens, furniture or ropes can be transferred directly from suspect to victim, victim to suspect or crime scene to suspect Example – Jeffrey Macdonald case study Fibers from his blue pajamas were found on the body of his wife

How are fibers left or picked up at a crime scene? Secondary transfer – victim has picked up fibers from another source and then transferred fibers to suspect (or from original source to suspect to victim) Example: Wayne Williams case study Fibers from his carpet were transferred to him and then transferred to victims’ bodies

Fiber collection Only collect fibers you wouldn’t expect to see at the crime scene If the victim had wall-to-wall orange carpeting and there was an orange fiber on the body, you wouldn’t examine that fiber Use special vacuum, sticky tape or tweezers to collect fibers Package in separate coin envelopes or paper bindles; label Be sure to collect control samples from victim’s house, clothing, crime scene and suspect!!!

Characteristics for Comparison of Fibers Appearance and type Feel Weave pattern Thread count Infrared spectrophotometry – the wavelengths of light that the fiber absorbs Fiber burn test

Types of Fibers - Natural Natural fibers come from animals, plants and minerals that are mined from the ground Examples: Animal fibers: wool, cashmere, mohair, angora, silk Plant fibers: cotton, linen, ropes, twine Mineral fibers: asbestos Mohair sweater Asbestos insulation

Types of Fibers - Synthetic Man-made fabrics Examples: Rayon, acetate, nylon, polyester Can be mixed with a natural fiber Example: carpet Polyester jacket Carpet – made from plant material and acetate

Weave Patterns Plain Weave Twill Weave Basket Weave Single strands that alternate over and under Single strand goes over three strands and under one Double strands that alternate over and under