Forensic Science Questioned Documents

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Forensic ScienceQuestioned Documents

• Unit 4
• Day Three

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You should have back

• Handwriting assignment packet
• Turn in any missing work TODAY

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Getting Started, Thursday/ 12-6

• A ransom note has been delivered to a family of a
  missing child.
• How would the crime lab go about analyzing the
  note for clues to the writers identity?

4
What equipment is used in document analysis?

• Gas chromatograph--separates mixtures on the
  basis of their distribution between a stationary
  liquid phase and a moving gas phase.
• The results are called a chromatogram.
• .

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What equipment is used?

• Mass spectrometer--an instrument that connects to
  the gas chromatograph.
• The unique feature of mass spectrometry is that
  no two substances produce the same fragmentation
  pattern, thus producing individual
  characteristics.

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How is ink analyzed?

• Chromatography--physically separate mixtures of
  gases, liquids or dissolved.
• Types
• Gas Chromatography
• HPLC--high-performance liquid chromatography
• TLC--thin-layer chromatography
• Paper Chromatography
• Ink Catalogs US Treasury Dept. has a systematic
  catalog of inks according to their dye patterns
  using TLC
• Tagging programs that slightly changes the ink
  year by year for identification purposes

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Paper Chromatographywith Ink

• Two samples of black ink from two different
  manufacturers run using paper chromatography.
• Ink is added on line
• Solvent moves up the paper carrying the ink
  molecules with it

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Retention Factor (Rf)

• How to calculate
• Divide the distance ink travels by distance
  liquid travels
• Ink travels from LINE or DOT to solvent front
• Liquid travels from BOTTOM OF PAPER

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Todays Assignments

• Ink Chromatography lab- your group of 3 will be
  analyzing one pen. Youll be using water and then
  alcohol. PUT YOUR CHROMATOGRAPH in box top on
  front table to use next class period.
• Finish up Document analysis lab from last class
  period
• THESE are due on MONDAY