Credit: © 2008 RSC

As a method of detection, fingerprint analysis has a long history, but there is a constant demand for new techniques for print enhancement and imaging; prints left on certain materials are difficult to detect and in some cases the evidence can be easily destroyed. Now, Paul Kelly and co-workers from Loughborough University have followed up a serendipitous discovery that points to a new method of fingerprint detection1.

Kelly and co-workers have long been interested in the properties of disulfur dinitride and the polymers it forms, with their main interest being in the conducting properties of the polymer. However, the monomer is highly reactive and it was observed that it interacted with fingerprints on the glassware used in the laboratory. On investigating further, they found that fingerprints left on materials of various porosities reacted with the disulfur dinitride to form a dark-coloured polymer — the fingerprints then being easily visible to the naked eye. Only very small amounts of residue were necessary for the imaging technique to be successful, and prints could be obtained from paper after washing, and even from the casing of a spent gun cartridge after firing.

The team went on to show that residues from inkjet printing could also be detected — even paper that was separated from the original print by a further sheet of paper contained sufficient residue to be detected. As yet the apparatus used to produce the disulfur dinitride is non-portable, but the versatility and sensitivity of the technique make it a viable alternative.