Hair Evidence Human or non- human? Body part origin (scalp, pubic, limb) Forcibly removed? DNA on root tissue Microscopic Examination.

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Presentation transcript:

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