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Development and Collection of Prints

Development and Collection of Prints. Patent Prints. What would you do if you found this on the wall of a crime scene?. Photograph: With scale (ruler) Multiple angles and distances Lift using clear plastic tape. Document, document, document! Store as evidence. . Plastic Prints.

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Development and Collection of Prints

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  1. Development and Collection of Prints

  2. Patent Prints • What would you do if you found this on the wall of a crime scene? • Photograph: • With scale (ruler) • Multiple angles and distances • Lift using clear plastic tape. • Document, document, document! • Store as evidence.

  3. Plastic Prints • What about this print? • Photograph: • With scale (ruler) • Multiple angles and distances • Take a cast using plaster of paris or other substitute (dental stone). • Document, document, document! • Store as evidence.

  4. Latent Prints Nonporous Surfaces Surfaces such as laminated or painted wood, tile, plastic, glass, tvscreens, metal, firearms, cars… • Dust with Powders: • Adheres to oils, sweat, etc. • Magnetic powder • Carbon black, aluminum powders • Fluorescent powders • ALS • Lift with tape; place on backing card of appropriate color • Document!!!

  5. Latent Prints Nonporous Surfaces • Cyanoacrylate Vapor (Super glue): • Best on plastic, metal, glass. • Heat superglue in airtight chamber with water source, vapors settle on amino acids producing polymer and permanent white print.

  6. Latent Prints Porous Surfaces Unlaminated or painted wood, paper, cardboard, cloth Multiple methods based on target surface 1. Iodine fuming: Best on paper or cardboard or unpainted surfaces. Place print in airtight container with solid iodine. Iodine vaporizes (sublimation: skips liquid phase) and settles on carbohydrates in sweat. FADES QUICKLY: Have to make permanent with starch solution.

  7. Porous Surfaces Latent Prints • Ninhydrin: • Best on paper • Spray surface with Ninhydrin spray and place in fume hood. • Reacts with amino acids (protein monomers) in sweat.

  8. Latent Prints Porous Surfaces • Silver Nitrate • Best on wood and styrofoam. • Reacts mainly with NaCl in our sweat to form silver chloride creating black or reddish-brown print under UV light.

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