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Fibers

Published on Nov 29, 2015

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PRESENTATION OUTLINE

FIBER ANALYSIS

BY: JESSICA HOGLE

FIBER EVIDENCE

  • Fibers left (in most cases) when there is human to human contact
  • Hope to trace to offender
  • Class evidence (can't direct back to one person)
  • Other factors need to be involved to convict

HOW TO COLLECT

  • collect using tweezers, tape, or a vacuum
  • Usually from carpet, furniture, blankets, ect

NATURAL OR SYNTHETIC

  • First determine if natural or synthetic
  • Natural: plants (cotton) or animals (sheep)
  • Synthetic: man made (rayon, acetate, polyester)

COMPOUND MICROSCOPE

  • Uses reflected light
  • Magnified through series of lenses

COMPARISON MICROSCOPE

  • Two compound microscopes
  • Joined by optical bridge
  • Used for precise identification

SPECTOMETER

  • Separate light into component wavelengths
  • Resulting lines=absorption lines
  • Measures light intensity

MICROSPECTROPHOTOMETER

  • Locates minute traces
  • Shows how light interacts with material
  • Link to computerized spectrophotometer for more accuracy
  • Increases number of identifying characteristics

ANALYSIS

  • First compare color and diameter
  • If similar, use chromatography for further analysis

CLASS EVIDENCE

  • Compared shape, dyes, chemical composition ect
  • If with all this, it's still class evidence
  • Same fibers can have different state of origin