1. Processing and Recovery of Fingerprint Evidence

2. Types of Fingerprint evidence that can be found:
Plastic – Fingerprints impressed in a soft substance such as wax, soap, putty, or dust.
Visible – Fingerprints left by fingers that have been coated with a colored substance such as ink or blood.
Latent – “Hidden” fingerprints that must be developed.

3. Latent Fingerprints Latent prints contain:
Perspiration (secreted by the pores in the friction ridges)
Moisture
Sodium chloride
Amino acids
Other substances
Body oils (acquired by contact with other parts of the body, such as the face or hair)
Dead epidermal cells and foreign substances

4. Finding Prints Points of entrance and exit
Objects or surfaces that may have been disturbed during the crime
Avoid handling objects if possible
Handle only by surfaces that are unreceptive to fingerprints
Fingerprint expert gets priority on objects such as firearms and documents
Correctly label and transport to prevent destruction

5. Flashlight and Magnifying Glass used to find fingerprints
Place flashlight at acute angle
Laser can be used
RUVIS – Reflected Ultraviolet Imaging System – ultraviolet rays can reveal fingerprints that were previously undetected

6. Processing Prints
Plastic or Visible print should be photographed first.
Latent print should be developed as little as possible, then photographed.
Print is then taken to lab (on object if possible)

7. Methods for Developing Latent Prints
Nonporous surface
Powder (dust with brush or magnetic powder)
Cyanoacrylate fuming (super glue)
Vapor adheres to latent residue upon condensing, building up and hardening the ridges.
Follow by dusting or adding chemical dyes
Photograph before lifting
Use adhesive tape to lift print

8. Porous Surfaces (paper, cardboard, unpainted wood)
Ninhydrin – reacts with amino acids
Sprayed on – amino acids turn purple
Silver Nitrate – reacts with sodium chloride and light
Paper is soaked in AgNO3 – turns brown
Iodine – combines with oils in print
Turns red-purple. Fades over time, so print must be photographed immediately
Prints on dead bodies can be developed with cyanoacrylate

9. Procedure for Lifting Fingerprints with Iodine
Place piece of paper containing fingerprint into ziploc bag without opening.
Place one small scoop of iodine crystals into the bag and immediately zip the bag.
Gently shake the bag for 5-10 minutes, or until the print is visible.
Remove paper from bag and immediately zip bag. Prevent any iodine from escaping the bag as a solid or vapor.

10. Procedure for Lifting Fingerprints with Iodine (continued)
Compare fingerprint with known fingerprints.
Match minutiae (minimum 10 points)