The test will allow about 40% more DNA samples to be identified

The Forensic Science Service (FSS) is piloting a computer-based analysis system which can interpret previously unintelligible DNA samples.

It claims the technique is a world first which will boost its crime detection rates by more than 15%.

The method is being tested by the West Yorkshire, South Yorkshire, Northumbria and Humberside police forces.

It allows scientists to pinpoint DNA samples when more than one individual has touched a surface, where only small amounts of DNA have been left behind or only poor quality material was found.

We think we can boost the success rate or our ability to pass on new leads to the police by around 10% Paul Hackett Forensic Science Service How DNA works DNA in 3D

FFS DNA manager Paul Hackett told BBC News the pilot scheme "aims to show how we can deploy that and put that in the police hands so that they can use it effectively.

"This particular technique is based on the foundations of existing DNA profiling technology so the laboratory-based techniques are exactly the same as we have used over the last 10 years, so that's very robust, very well established.

"This application is a piece of software, along with a forensic scientist, that can help us interpret previously complex, mixed DNA profiles that the forensic scientist really couldn't interpret."

'Cold cases'

FSS scientists believe the technique, called DNAboost, could be the key to countless "cold cases" which have lain dormant in police files.

HOW POLICE USE DNA DNA samples taken from blood, hair, semen, etc at crime scene Sample used to produce unique DNA profile of criminal Profile helps identify criminal's physical characteristics Suspects can be tested for DNA match with crime scene Existing 3.5m samples on DNA database also checked Mass DNA screenings of village, school, etc may be used Chance of two people having same DNA - one in one billion

Mr Hackett said the system could potentially have an impact on both "cold cases" and future trials.

"The beauty of this technology is it's both retrospective and we can apply it on future cases," he said

"So the technique it's best applied to was introduced a decade ago - the Forensic Science Service has tested over half-a-million cases in the last 10 years - and we think we can boost the success rate or our ability to pass on new leads to the police by around 10%.

"So that's tens of thousands of cases going back into history. If we look forward then we can apply it to cases that are coming into the lab from today."

The pilot will run for three months, after which it is due to be extended to remaining police forces.

Det Sgt Kevin Morten, head of scientific support services at South Yorkshire police, told the BBC: "If an offender enters a crime scene and touches a surface they will leave a small trace of DNA; the next person who's in that scene, or has been in previously, will also leave small traces of DNA.

"Previously we have not been able to split those profiles, but with this technique we'll be able to do that and that will assist us greatly in further detecting crime".

The FSS can already handle more than 10,000 DNA crime stain samples each month and about 50,000 DNA samples from individuals.

IMPACT OF DNA ON CRIME DETECTION
CRIME	NATIONAL DETECTION RATE	DNA DETECTION RATE
All recorded crime	26%	40%
Domestic burglary	16%	41%
Non-domestic burglary	11%	50%
Theft of vehicle	15%	24%
Theft from vehicle	8%	63%
Criminal damage	14%	51%
Source: Home Office (04/05 figures)