1. Fingerprint Detection and Processing Fingerprint 2

2. Fingerprints as Evidence Three forms –Visible prints Found with the naked eye Made after ridges come in contact with a colored material –Plastic print Left on a soft material like putty, wax, etc. –Latent Left after body perspiration or oils touch the surface of an object

3. Processing Techniques Fingerprint “lifting” consists of many techniques from the simple to the very complex Technique used is dependent upon the type of material, quality of print and environment Many techniques (esp. chemical) are temporary and must be photographed immediately

4. Processing Techniques Powder –Among the most common and easiest to use –Powders come in dark and light forms Correct choice depends on the color of the surface –Uses dusting brush Lightest touch must be applied Powder evenly spread over the print Powder will stick to the oils in the print –Print is lifted with ordinary cellophane tape

5. Processing Techniques Iodine Fuming –Oldest chemical technique –Iodine crystals sublimate in air –Will react with either the perspiration or fatty oils in the print (still not clear which is correct) –Very effective especially if heated inside a fuming chamber –Must be photographed immediately since prints will fade rapidly Can be “fixed” with a 1% starch solution A laboratory-grade fuming chamber Note: Iodine fumes are poisonous and should not be inhaled

6. Processing Techniques Ninhydrin –A chemical that reacts with amino acids in perspiration Reveals purple/blue prints Usually sprayed on the object –Development may take several hours –Technique has been used successfully on 15 year old fingerprints –Very good for lifting prints from paper, cardboard Note: Ninhydrin solutions are mildly poisonous and exposure should be minimized.

7. Processing Techniques Cyanoacrylate –Commercial super glue –Will produce fumes if heated or dripped on to a cotton ball treated with sodium hydroxide –Fumes will “stick” to latent prints revealing a white colored print Very popular due to ease of obtaining materials –Especially useful on metals, leather, electrical tape, plastic bags Note: Super glue fumes are poisonous and flammable in high concentrations.

8. Processing Techniques Other techniques –Additional chemical techniques exist for almost every kind of surface –Use of polarized light, UV fluorescence –Lasers