A new way to interpret DNA samples has been announced by the Forensic Science Service. Some high-profile cases have been solved by DNA evidence:
LYNDA MANN AND DAWN ASHWORTH
The first murder conviction using DNA evidence came in 1988 when baker Colin Pitchfork was found guilty of the separate murders of two schoolgirls - Lynda Mann and Dawn Ashworth, both 15 - in Narborough, Leicestershire.
Advancements in DNA technology led to Pitchfork's conviction
Both of the cases - one in 1983 and one in 1986 - involved sexual assaults, and semen samples were taken from both bodies.
Police had been convinced that local man Richard Buckland had committed both crimes and, under questioning, he confessed to the later murder but said he had no involvement in the first.
It was because of officers' belief that Mr Buckland had killed both girls that Leicester University's Dr Alec Jeffreys, who had developed a technique for creating DNA profiles, was called in.
After comparing semen samples with Mr Buckland's blood sample, Mr Jeffreys conclusively proved that both girls had been killed by the same man, but that it had not been Mr Buckland.
After the world's first mass screening for DNA - where 5,000 men in three villages were asked to volunteer blood or saliva samples - Pitchfork was eventually caught and jailed in 1988.
On 14 July 2001, Bradley Murdoch, of Broome, Western Australia, flagged down British backpackers Peter Falconio and Joanne Lees in their camper van in Alice Springs.
Murdoch consistently denied responsibility for the killing
He shot Mr Falconio dead and pointed a gun at Miss Lees before tying her up. She later escaped.
During the investigation that followed, the UK's FSS team carried out DNA tests on hand ties used on Miss Lee.
A DNA profile was obtained from "deep inside the home-made ties" thanks to the relatively new technology of DNA Low Copy Number (DNA LCN).
DNA LCN means DNA profiles can be obtained from samples containing only a few cells, as with the hand ties.
In 2005, in the court case that led to Murdoch's conviction, the jury heard that the genetic sample obtained from the handcuffs was 100 million times more likely to have come from Murdoch than anyone else.
In 1981, Marion Crofts, 14, was dragged from her bicycle as she rode to band practice in Aldershot, Hampshire, and beaten to death. She had also been raped and strangled.
Marion Crofts was killed in 1981
Despite a major investigation, it was not until two decades later, and thanks to advances in forensic evidence gathering, that there was a major breakthrough.
In July 1999, a full DNA profile of Marino's killer was obtained using DNA LCN.
It was extracted from microscope slide samples which had been taken from Marion's body and sealed in 1981. The process was risky - if the tests had failed, the samples could not be used again.
The DNA profile was entered into the national DNA database, but there were no matches.
In April 2001, Leicester man Tony Jasinskyj was arrested and charged for allegedly assaulting his wife. He was routinely swabbed for DNA and the profile entered into the database.
It turned out to be a match for the profile of Marion's killer and he was subsequently jailed for life in 2002.
Michael Little, 53, died when a brick smashed into the cab of his 40-tonne lorry as he drove on the M3 in Surrey in March 2003.
Craig Harman admitted manslaughter after giving DNA
DNA taken from a brick thrown through Mr Little's cab was checked against the national database.
A relative of Craig Harman, of Frimley, inadvertently led police to their man after officers used the pioneering familial searching technique.
Familial searches, which are based on the fact that individuals who are related are more likely to have similar DNA, had been launched a few months before.
The DNA profile from the brick was checked against the national database, but because Harman did not have a criminal record no match came up.
Using the technique, 25 people with similar DNA were located and Harman's relative was top of the list. Harman was then caught after giving a DNA sample which matched exactly.
In April 2004, Harman, then 19, pleaded guilty to manslaughter, becoming the first person in the world to be successfully prosecuted using familial searching.