"Bullet fingerprinting" technology has taken another step forward, university researchers announced yesterday.

"Bullet fingerprinting" technology has taken another step forward, university researchers announced yesterday.

The technique of "visualising" fingerprints from metal surfaces, such as fragments of bullet casing, has already proved a huge success in the world of forensic investigation.

Developed by Dr John Bond of Northamptonshire Police Scientific Support Unit in collaboration with scientists from the University of Leicester, it allows scientists to find prints even after they have been removed.

The discovery was named last year as one of Time Magazine's top 50 inventions of the year and Dr Bond's assistance has already been sought by police forces across the world to crack "cold cases".

Yesterday researchers at the university's chemistry department announced developments in the technology, uncovering new ways of recovering prints from metal surfaces.

Researcher Alex Goddard has uncovered a natural technique that he believes is so simple it has been overlooked until now.

It involves studying chemical and physical interactions between the metal and fingerprint sweat deposit.

Using advanced surface imaging techniques, nanoscale observations of fingerprinted brass samples can identify the optimum conditions to promote the natural enhancement of the fingerprint and improve the recovery rate.

It has also been proven that components of the sweat deposit survive washing and wiping of the surface.

Mr Goddard said: "Once a finger has touched the metal surface, a residue remains behind. This starts to react with the metal and an image of the fingerprint can be developed by use of elevated temperature and humidity, with the resultant image becoming a permanent feature on the surface of the metal.

"Currently, fingerprint recovery from bullets is very low; less than 1%.

"This new technique promotes a naturally occurring process which does not involve adding anything to, or damaging, the evidence."

Mr Goddard recently presented his findings at the University of Leicester's Postgraduate Research Festival.

Dr Bond, also an Honorary Research Fellow at the university's Forensic Research Centre, added: "I am delighted that this research in the chemistry department is producing really interesting and useful results."