1. Fingerprints: Methods of Detection

2. Crime Scene Fingerprints
Visible/Patent Prints – Fingerprints made when the finger leaves a visible material
Plastic Prints – Fingerprints that leave an impression on a soft material
Latent Prints – Invisible fingerprints

3. Locating and Visualizing Prints
Depend on the type of surface
Hard/Nonabsorbant surfaces
Glass, mirror, tile, painted wood
Soft/porous surfaces
Papers, cardboard, cloth
RUVIS – Reflected Ultraviolet Imaging System

4. RUVIS UV light identifies prints on non-porous surfaces
UV light absorbs print
UV light is reflected back to the viewer as green light

5. Methods of Visualization
Physical Methods
Fingerprinting powder
Chemical Methods
Iodine fuming
Ninhydrin Super glue fuming

6. Fingerprint Powder Powder is applied lightly with a brush
Select the color of the powder that gives you the best color contrast with the surface being dusted
Gray powder – aluminum dust
Black powder – carbon or charcoal
Fluorescent powder
Powder adheres to perspiration residues or body oils left on the surface
Magnetic fingerprinting powder

7. Iodine Fuming Oldest chemical method Procedure Not permanent
Put fingerprint surface in a chamber with solid iodine crystals
Heat solid iodine to the vapor state
Vapors fill the chamber and combine with the latent print to make it visible
Not permanent
PHOTOGRAPH print to keep a permanent record!

8. Ninhydrin Apply to porous surfaces
Ninhydrin attaches to amino acids present in perspiration
Prints usually appear in 1-2 hours

9. Super Glue Fuming Used on non-absorbent surfaces
98-99% cyanoacrylate ester
Procedure
Put super glue on a cotton ball
Place cotton ball and print surface in a chamber for up to 6 hours
Interacts with and adheres to the latent print making it visibly white

10. Preservation
Once the latent print has been visualized, it must be permanently preserved for future comparison in court
Photographs must be taken
Preserve image
Show’s location with respect to other evidential items at the crime scene

11. Preservation Small objects Large immovable objects
Print preserved in entirety
Cover print with cellophane
Large immovable objects
“Lift” print with tape
Place tape on labeled card

12. Fingerprint Enhancement
Lifted prints are not usually in perfect condition
Digital Imaging Software can enhance fingerprints for the most accurate and comprehensive analysis
Scan print into digital file
Change brightness, contrast, filters
Comparison function

13. AFIS
Automated Fingerprint Identification Systems: Computer that uses automatic scanning devices to convert the image of a fingerprint into digital minutiae that contain data showing the ridges at their points of termination and the branching ridges.
Position and orientation of minutiae are determined to convert the fingerprint into a geometric pattern

14. AFIS
A set of 10 fingerprints can be searched against a file of 500, finger in 8/10 of a second
Computer produces a list of prints that have a high degree of correlation
Selected prints are examined by a trained fingerprints expert
Any AFIS user can exchange data with any other AFIS user