Latent Fingerprinting Techniques

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Latent Fingerprinting Techniques

• Above metal gray print lifted on golf ball

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Overview

1. Magnetic carbon powders
2. Fluorescent powders
3. Cyanoacrylate (superglue)
4. Ninhydrin
5. DFO
6. Gentian Violet
7. Iodine
8. Small Particle Reagent (SPR)
9. Sudan Black and Amido Black
10. Microsil

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A. Magnetic carbon powder

• Adhere to powder and fatty deposits
• Used on dry, smooth surfaces
• Right magnetic applicator and
• black carbon powder

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B. Fluorescent powders

• Useful with confused backgrounds where black
  powder cannot be seen
• Below Fluorescent powder used on
• confused background
• Right Instant
• white powder
• on metal
• toolbox

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C. Cyanoacrylate fuming

• Superglue heated and fumes adhere to print
• Creates white residue FP
• Dyes (basic yellow and ardox) used to enhance
  visibility
• Excellent on styrofoam,
• aluminum and plastic bags
• Right superglue print on aluminum foil,
• stained with Ardox

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1. Left Superglue heated on
hot plate to create fumes

• 2. Right items
• placed in fume
• chamber
• 3. Left White reside print stained
• with basic yellow dye for
• better visibility

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D. Ninhydrin

• Reacts with Amino acids to create purple FP
• Reaction called Rhuemanns purple
• Especially useful on porous surfaces, like paper
• Right Developed Ninhydrin print
• on left and placed into AFIS
• system to find match

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E. DFO (Ninhydrin analog)

• Reacts with amino acids and useful on paper
• Useful with contaminated objects (grease etc.)
• Only visible with green/blue light source
• Right Ninhydrin
• print on right, DFO
• print not seen on left
• Left Using green
• light and red filter,
• DFO print is now
• visibile on left

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F. Gentian violet

• violet dye stains fatty sebaceous sweat
• Useful on duct tape and sticky surfaces
• Right purple print lifted
• off the backside of tape

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G. iodine

• Iodine crystals give off vapors that attach to
  oils, creating a brown residue FP
• Works best on fresh prints
• Benzoflavone makes the print more visible
• Right Iodine print on left, benzoflavone dye
• stains the print a dark blue

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H. Small particle reagent (SPR)

• Molybdenedisulfide (MoH2S) powder in water
• used on wet and/or dirty/greasy surfaces
• L/R Wet surface is
• sprayed with SPR
• and lifted with
• gelatin paper

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I. Amido Black and sudan Black

• Amido black stains the proteins in blood
• Right Bloody footprint stained black/
• blue using Amido Black
• Sudan black used to stain
• after cyanoacrylate fuming
  
• Also used for direct staining
• Above direct staining on plastic cup using Sudan
  Black

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J. Microsil

• Casting agent hardening agent
• Pliable cast used for FPing cadavers and rough
  surfaces
• Right Microsil cast impression of
• ridge lines from a fingerprint