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Forensic Science Questioned Documents

Forensic Science Questioned Documents. Devices. Getting Started. 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 writer’s identity?. What equipment is used in document analysis?.

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Forensic Science Questioned Documents

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  1. Forensic ScienceQuestioned Documents Devices

  2. Getting Started • 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 writer’s identity?

  3. 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. • . 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.

  4. 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

  5. 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

  6. 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

  7. Today’s Assignments • First you will practice calculating Rf • Ink Chromatography lab- your group of 3 will be analyzing one pen. You’ll be using water and then alcohol. PUT YOUR CHROMATOGRAPH in box top on front table to use next class period.

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