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