Chemical Make-up of Fiber FT-IR: –Fourier-Transform Infrared Spectro. –Absorption of Infrared...
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Transcript of Chemical Make-up of Fiber FT-IR: –Fourier-Transform Infrared Spectro. –Absorption of Infrared...
Chemical Make-up of Fiber
• FT-IR: – Fourier-Transform Infrared Spectro.– Absorption of Infrared light by the polymer that
comprise fiber result in characteristic pattern– Non-destructive
FIBER MATCHES
Collection of Fiber Evidence
• Relevant articles of clothing packaged in paper bags– Items must be packaged separately
to prevent cross contamination
• Any weapons with trace should be packaged correctly
• Collection of fibers using a tape-lift may be useful• In the lab, several units may collaborate to analyze
item – (ex: bullets containing trace)
Case File: Fibers on Scissors
• Sexual Assault Case
• Suspect used his scissors to cut off victim’s clothing
• Scissors recovered in search warrant
Case File: Fibers on Scissors
• Fibers tape-lifted off scissors
• Mounted and viewed microscopically
• Fibers from all victim’s clothing located: red acrylic, blue polyester and spandex (bra)
Paint Evidence
• General components of paint– Pigments and several additives suspended in a
BINDER – Binder provides the medium for the pigments
and is a polymeric substance
PAINT ANALYSIS
• Most important components of paint in forensic analysis:– color– Structure of different layers
** The most important physical property of
paint analysis is layer structures
** Can be individualized to a single source if there is sufficient detailed layer structure
Automotive Finishing
• For Steel requires at least four organic coatings:– Electrocoat Primer– Primer Surface/ corrosion control– Basecoat/ provides color coat– Clear Coat/ improves gloss