Download Fingerprinting Techniques

• Latent prints – invisible
• Use – 1. high-intensity UV light
2. dusting – finely ground powders stick to
fingerprint residues, lifted with tape, attached to labeled
card – best on fresh prints
On nonporous substances
1. Cyanoacrylate fuming (super
glue)
- reacts with proteins and fatty
acids in print when heated
- item suspended in enclosed
fuming chamber w/ warmed water
- glue placed in small container
inside chamber & heated
- fumes react with print, print 
whitish color
2. Silver Nitrate (AgNo3) solution
- reacts with salts in sweat in print forming silver
chloride (AgCl2) – appears black in UV light
On Porous surfaces
Ninhydrin
- reacts with amino acids in print – turns purple
- spray or dip item in ninhydrin – 48 hours to develop
(faster if heated)
1.
2. Diazofluoren (DFO)
- paper dipped in DFO for 10 sec, dry, repeat
- reacts with amino acids
- visible under blue-green light
On NonMetal surfaces
Vacuum metal deposition
- chamber evaporates gold & zinc
- gold attracted to thin layer of tissues left by print, zinc
condenses on gold coating and b/t ridges
Fingerprint Database
 Prints – photographed, scanned, digitized
- for comparisons
 FBI – Integrated Automated Fingerprint Identification
System (IAFIS)