FIBER ANALYSIS

KEY POINTS

• Fiber analysis can't be used to trace absolutely a offender as DNA or fingerprints.
• Trace evidence may not be as strong for evidence as DNA or fingerprints but it has it's place.
• Cross transfers occur when people come in contact.
• This is what investigators hope to happen so that they can trace the origin and the offense and maybe even the offender.
• The problem with fiber evidence is that fibers are not unique. Unlike fingerprints or DNA, they cannot pinpoint an offender in any definitive manner. There must be other factors involved, such as evidence that the fibers can corroborate or something unique to the fibers that set them apart. For example, when fibers appeared to link two Ohio murders in the 1980s, it was just the start of the case.

KEY POINTS

• Orange fibers in her hair looked suspiciously like those that had been found on a twelve-year-old female murder victim from eight months earlier in the same county.
• The shape, color, and size and type of fiber are also important.

KEY POINTS

• Since they were made of polyester and were oddly shaped (trilobal), forensic scientists surmised that it was carpet fiber. In addition, a box found near Kristin's body and plastic wrap around her feet indicated that the killer had once ordered a special kind of van seat, but then leads dried up.
• The carpet was used to carry the body.

KEY POINTS

• For analysis, they are first determined to be natural, manufactured, or a mix of both.
• These are the methods to determine what type of fiber they are.

KEY POINTS

• Fibers are gathered at a crime scene with tweezers, tape, or a vacuum.
• These are important because they show how to collect fiber evidence.

KEY POINTS

• Natural fibers come from plants (cotton) or animals (wool). Manufactured fibers are synthetics like rayon, acetate, and polyester, which are made from long chains of molecules called polymers. To determine the shape and color of fibers from any of these fabrics, a microscopic examination is made.
• These are how natural fibers are classified.

KEY POINTS

• In short, the fiber analyst compares shape, dye content, size, chemical composition, and microscopic appearances, yet all of this is still about "class evidence."� Even if fibers from two separate places can be matched via comparison, that does not mean they derive from the same source, and there is no fiber database that provides a probability of origin.
• Fiber analyst is very important for comparing fibers.

KEY POINTS

• Generally, the analyst gets only a limited number of fibers to work with sometimes only one. Whatever has been gathered from the crime scene is then compared against fibers from a suspect source, such as a car or home, and the fibers are laid side by side for visual inspection through a microscope.
• Fibers are usually limited.

KEY POINTS

• A compound microscope uses light reflected from the surface of a fiber and magnified through a series of lenses, while the comparison microscope (two compound microscopes joined by an optical bridge) is used for more precise identification.� A different device, the phase-contrast microscope, reveals some of the structure of a fiber, while the various electron microscopes either pass beams through samples to provide a highly magnified image, or reflect electrons off the sample's surface.� A scanning electron microscope converts the emitted electrons into a photographic image for display.� This affords high resolution and depth of focus.
• The compound microscope can be very helpful as it sees through the fiber.