London: Scientists have developed a new system for visualising "hidden" crime scene fingerprints.
Despite several enhancement techniques already in use, only about 10 percent of fingerprints from crime scenes are of sufficient quality to be used in court.
The technique is based around fluorescent chemical "tags" and works on metal surfaces, meaning it could be used on knives, guns or bullet casings, the BBC reported.
Although the technique currently works only with metallic objects, co-author Prof Robert Hillman, from the University of Leicester said these were "quite significant" forensically - especially in violent crimes.
The classical approach to enhancing the visibility of hidden, or - to use the correct forensic terminology - latent, prints is to apply a coloured powder that adheres to the oily residue left by the finger surface.
The new technique visualises fingerprints by exploiting the fact that their ridges do not conduct electricity.
Here, the fingerprint material acts like a stencil, blocking an electric current that is used to deposit a coloured film.
The film is directed to the regions of bare surface between the ridges of a fingerprint, thereby creating a negative image of the print.
The substances used to do this are "electrochromic", which means they change from one colour to another when subjected to an electric voltage.
The researchers say the technique is highly sensitive, as even tiny amounts of insulating residue, just a few billionths of a metre, can prevent the coloured film from sticking to the metal below.
As a result, much less fingerprint residue is required than is typical for other techniques.
Also, because it focuses on the gaps between the fingerprint ridges, it can be used in combination with existing, powder-based approaches.
ANI
