Swiss scientists have developed a way to detect fingerprints by measuring the chemical traces they leave on a surface. Using a scanning electrochemical microscope (SECM) to detect invisible traces of sweat and natural skin oils, the team created a chemical picture of a fingerprint.

The advance comes from a team led by Christophe Champod from the University of Lausanne and Hubert Girault at the Ecole Polytechnique Fédérale de Lausanne. They hope their method will make it possible to read fingerprints from textured or illustrated surfaces, such as banknotes, plastic and paper, and from wet surfaces. Conventional fingerprinting methods rely on optical detection and do not work well on surfaces like these.

An SECM has a very fine tip which can detect chemical changes on a surface. The team exposed the fingerprints to gold nanoparticles, which stick electrostatically to the skin secretions. They then added a layer of silver on top of the gold to help improve the contrast between the fingerprint and the background.

Claude Roux, Director of the Centre for Forensic Science at the University of Technology Sydney, is confident that the method 'has the potential to develop fingermarks on surfaces that are known to generate poor results with current techniques. In other words, latent fingermarks that remain undetected with current techniques could be made visible when using this method.'

The method 'could provide significant advantages for fingermark detection on a range of difficult surfaces,' agreed Chris Lennard, professor of forensic studies at the University of Canberra. 'However,' he cautioned, 'before such an imaging technique could be readily applied on items submitted for examination, the technology would need to improve so that larger areas can be scanned within a much shorter period of time. At present, the technique would be impractical for use in routine casework.'

Clare Boothby