Collecting fingerprint evidence requires different techniques depending on whether the surface is porous or non-porous. 'Porous surfaces', such as paper, cardboard, or unfinished wood, absorb fingerprints, making them more challenging to develop. The primary technique for porous surfaces is chemical processing. One common method is the use of iodine fuming, where the object is exposed to iodine vapors, which react with the oils in the fingerprint to create a temporary brown image. Another method is ninhydrin, which reacts with amino acids in the fingerprint to produce a purple-blue image. Ninhydrin is often used after iodine fuming because it develops fingerprints that iodine may not reveal. Another chemical is DFO (1,8-Diazafluoren-9-one), which is similar to ninhydrin but reacts more sensitively, producing a fluorescent image t....
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