Page last updated at 15:56 GMT, Monday, 23 March 2009

New DNA test gives cold case hope

DNA
Forensic scientists say they are excited about the new technique

A new technique which can decipher previously unintelligible DNA samples has been made available to all police forces in England and Wales.

The Forensic Science Service (FSS) said the DNAboost method might shed light on "many thousands" of unsolved cases.

It allows scientists to obtain individual DNA profiles from crime scenes which contain a mix of genetic material from several people.

But some experts have warned that it could lead to miscarriages of justice.

During the pilot, DNAboost was used on about 2,000 samples in four police forces - Humberside, Northumbria, South Yorkshire, West Yorkshire.

The FSS said it helped police to identify suspects and build evidence for cases, and was now "fit for purpose" to be used by all forces.

'Cold cases'

Previously, it was impossible for scientists to accurately separate out DNA from different individuals at one crime scene, for example, where two or three suspects handled the same weapon.

Now, DNAboost can use computer technology to do just that and provide identifiable DNA profiles for each suspect.

These can then be checked against the national DNA database to try to find the culprit.

It is thought the technique could be of use in an estimated 10,000 criminal cases each year and scientists are already looking through "cold cases" - including unsolved rapes and murders - to see if it can be of benefit.

There will be many thousands of cases in our archives that could benefit from that technique
Martin Bill
Forensic Science Service

Experts say it could increase the number of provable cases by as much as 30%.

Martin Bill, research manager at the FSS, said scientists were very excited about its potential.

"We feel this approach is scientifically very sound and has low potential for false exclusion or inclusion," he said.

"There will be many thousands of cases in our archives that could benefit from that technique.

"We're hopeful that some will come to light over the coming weeks."

Forensic Scientist Mark Pearse told the BBC about one case which had utilised DNAboost to identify a suspect in a car-jacking.

After struggling with the car's owner, the offender fled the scene leaving a trainer behind.

A skin flake on the shoe was examined and found to contain more than one DNA profile, but the new technique was able to unscramble the sample and give police the identity of a suspect.

'Not foolproof'

But Prof Allan Jamieson, director of The Forensic Institute in Glasgow and former head of forensic science at Lothian and Borders Police, urged caution.

"Boost can come in useful when all you want to do is generate the possible contributors," he told the BBC News website. "But it doesn't tell you who the actual criminals are.

People think DNA can do no wrong, but that's not true
Prof Allan Jamieson
The Forensic Institute

"The danger is that because of the public's confidence in DNA, there's a real likelihood that you identify the wrong person because they just happen to match, or you get the crime scene results being interpreted to fit the suspect.

"People think DNA can do no wrong, but that's not true. It's not black or white, and it can be wrongly interpreted. Two scientists could interpret the same results differently."

Evidence given by Prof Jamieson casting doubt on the reliability of DNA testing was instrumental in the collapse of the Omagh bomb trial in 2007.

To illustrate his point about DNAboost, he said: "If I have profile AB and you have profile CD, our mixed cells would have a profile ABCD. However, the same profile could be produced by two people with profiles AC and BD, or AD and BC."

Anyone with profile BD, for example, who happens to live in the area, would then have to explain why he had no association with the crime scene, he added.

The FSS analyses DNA evidence from about 100,000 cases every year - about 10% of which involve mixed or poor quality samples where DNAboost could help.



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