Nick Stokes, Sarah Sidle and the gang on CSI should be glad to hear this – Israeli scientists have developed a new method for getting fingerprints from paper surfaces, that is claimed to get better results than existing technology.
Ordinarily, when investigators want to lift fingerprints from paper, they start by applying gold particles to the surface. If all goes well, the gold sticks to the amino acids in the sweat residue in the fingerprints. Silver particles are then added, which stick to the gold, resulting in a positive, low-contrast image of the print.
According to a research team from the Institute of Chemistry at the Hebrew University of Jerusalem, however, the variable composition of the sweat residue results in this process yielding usable prints less than half the times it is tried. In their new alternative method, the gold particles are made to stick to the paper, but not to the fingerprints – sebum, an oily bodily substance in the prints, keeps it from doing so.
The paper is then treated with a developer that contains silver. This causes the gold-covered paper to turn black, highlighting the fingerprint as a high-contrast white image – like a photographic negative.
Because sebum is present independent of sweat, the unpredictable variations in sweat residue composition is no longer an issue. The new technique can also be used on wet paper, as sebum tends to stay put when exposed to water. Amino acids, on the other hand, will dissolve and get washed away.
A paper on the research was recently published in the journal Angewandte Chemie.
Source: Wiley Online Library