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Fingerprint Developments

The magnifying glass and talcum powder of the traditional detective looking for fingerprints has been replaced by sophisticated chemistry and laser physics.

The perspiration that causes fingerprints is 99% water; it is the other 1% containing fatty acids, fats, urea, amino acids, salts, phosphates, carbonates and sulphates that interest forensic experts. Chemical reactions with one or more of these substances can produce visible fingerprints from invisible "latent" marks.

Lasers are being used to generate fluorescence in latent prints which have been treated with a variety of chemicals, most notably these days DFO (1,8-diazafluoren-9-one). Forensic experts at the Institute of Environmental Science and Research (ESR) are looking at developing new forms of DFO to increase its effectiveness and sensitivity over earlier compounds.

The methyl or ethyl cyanoacrylate esters in Superglue are useful in "fixing" fingerprints, according to ESR researcher Angela Lavis. Articles to be fingerprinted and a few drops of glue are put in a closed container. The ester vapours are absorbed by the fingerprint residue and a white, stable polymer is formed. This polymer can then be stained independently of the original surface on which the fingerprint rests.

Lavis says that one new development in this area is to simultaneously apply the dye and the glue in a one-step process, reducing the time required.