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Hair Evidence• Human or non-
human?• Body part origin
(scalp, pubic, limb)• Forcibly removed?• DNA on root tissue• Microscopic
Examination
FIBER EVIDENCE
• Commonly in incidents which involve personal contact:– Homicide
– Assault
– Sexual Offenses
• Anywhere there maybe a cross-transfer
Fiber Evidence
• Sources: apparel, bedding, carpet (flooring and automobile)
• Mixtures (gray sweatshirt =black rayon and white cotton)
• Dyes
Hair Evidence• Human or non-
human?• Body part origin
(scalp, pubic, limb)• Forcibly removed?• DNA on root tissue• Microscopic
Examination
FIBER MATCHES
Two Broad Groups
• Natural Fibers– Animal
• Wool, cashmere, fur (mink, rabbit...)
– Plant• Cotton
– Almost meaningless unless dyed and in a combination of colors
• Man Made Fibers– Derived from natural
or synthetic polymers
– Polymer is the basic chemical substance of all synthetic fibers
• Made of Monomers
FIBER ANALYSIS
• NATURAL FIBERS – derived from animal or plant sources
- animal comprise the majority of natural fibers seen in the laboratory (wool)
- most prevalent plant fiber is cotton
MAN- MADE FIBERS
• Regenerated fibers – manufactured from raw materials derived from cotton or wood pulp
- rayon
-acetate
-triacetate
• Synthetic fibers – manufactured from synthetic (man-made) chemicals- nylons, polyesters, and acrylics
* polymers – basic substance of all synthetic fibers
LABORATORY EXAMS
• Examinations vary so much from crime laboratory to crime laboratory and from analyst to analyst.
• Consistent forensic analysis:
- compare color
- compare diameter
* Scanning Electron Microscope
Examining Color & Diameter
• Under Microscope fibers may appear to have same color– However dyes applied by manufacture may have a
different composition– Microspectrophotometer
• Non destructive way to compare colors
• Various shapes / diameter – Trilobal fibers
• Presence or absence of a delustering agent – Titanium dioxide
LABORATORY EXAMS
• Dye components can be extracted from fibers and analyzed by Thin Layer Chromatography and distinguished from each other
** Normally fibers can be analyzed to
show class characteristics