hair evidence human or non- human? body part origin (scalp, pubic, limb) forcibly removed? dna on...

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