The scientist who invented DNA fingerprinting two decades ago warned yesterday that the huge expansion of the national database - which now contains details of 2.5 million criminals - could contain mistakes and lead to miscarriages of justice.
Professor Sir Alec Jeffreys said forensic specialists might not be using a sufficiently accurate DNA match when comparing suspects with forensic material retrieved from a crime scene. Only 10 different DNA markers were used on the database to distinguish between individuals, he said.
"If you have a database of 2.5 million people you will start having matches. The current DNA database uses 10 distinct markers and I think there is still a residual risk of a false match. They should use about 15 markers because otherwise it leaves open the possibility that the match from the crime scene sample is genuine but a fluke."
He also warned that if the police kept profiles of suspects who were later cleared - which they can now legally do - that could lead to a disproportionate representation of minority ethnic groups, especially in the major cities, on the database.
Sir Alec was working in a laboratory at the University of Leicester on 10 September 1984 when he stumbled across the key to the future of genetic research and development. He found a stretch of DNA that is unique to every individual (except identical twins). The findings have had effects on criminal cases, paternity, immigration and conservation as well as led to life-saving developments in medical research.
Genetic "fingerprints" exist in blood, bone, hair follicles, saliva, semen, skin and sweat. They are the same in every cell and retain their distinctiveness throughout a person's life.
His discovery led to the establishment of the British DNA database, the biggest in the world with more than 2.5 million profiles from criminals and suspects, and more than 200,000 DNA samples from unsolved crimes, including blood and semen stains. The Home Office says the database is being used on average to link suspects to 15 murders, 31 rapes and 770 car crimes every month.
The ability of forensic specialists to retrieve DNA from ever smaller crime samples has enabled the police to re-examine unsolved cases dating back 30 years and convict the guilty. As a result of its success the Government is giving the police greater powers to retain samples taken from anyone who has been arrested and from people who have given material voluntarily.
A new forensic technique developed in the US has also helped Scotland Yard identify the ancestral origins of an offender for the first time. Sir Alec also believes that techniques will be further developed in the future so more details on a how a person looks will be gleaned from a DNA extract. Genetic fingerprinting could allow police to determine the eye colour, hair colour and even facial features of criminal suspects, he said yesterday. Scientists can already identify samples from people with red or ginger hair.
He said: "The research is at the science fiction stage but our physical appearance is largely determined by our genetic make-up.
"The problem is that facial features depend on age, and if you have not got the age it will be very complicated. Also some of the variations behind these genes will lie behind severe clinical problems. The police would then be accessing information of profound medical significance and I would argue the police have no right to access such information."
Sir Alec said the application of the fingerprint technique that gave him most satisfaction was its use in immigration disputes. "These families have done nothing wrong whatsoever. The fact that we have managed to bring thousands of them back together makes me very proud," he said.
He welcomed the idea of a global database containing DNA information on every individual but said that police should not have access to the profiles unless the people had been convicted of a criminal offence.
Commenting on his discovery in Leicester 20 years ago, Sir Alec said: "I regard this as a wonderful triumph of British science. We have consistently led the world in the application of DNA."
FIGHTING CRIME
Francisco Arce Montes
Thanks to DNA fingerprinting, Caroline Dickinson's killer was finally brought to justice eight years after the teenager was raped and murdered in a French youth hostel. Samples from the crime scene proved the guilt of Montes, an itinerant Spaniard. He was sentenced to 30 years in prison in June 2004.
Richard Baker
Baker was a DJ suspected of raping hundreds of young women in Britain and Spain. Police launched a manhunt after the attacks were linked by DNA. Baker, 34, from Bodmin, Cornwall - already jailed for rape - was named as a suspect by his brother. He was arrested trying to flee the country. DNA proved five of the charges against him and he was given four life sentences in 1999.
Roy Whiting
Whiting snatched eight-year-old Sarah Payne in July 2000 while she was visiting her grandparents at Kingston Gorse, West Sussex. The 42-year-old mechanic, from Littlehampton, bundled Sarah into his van as she walked home from playing in a nearby field. Her body was found 17 days later. DNA tests showed that a hair on Whiting's sweatshirt came from Sarah. Whiting was jailed for life in December 2001.
James Hanratty
Hanratty was hanged in 1962 for murdering the civil servant Michael Gregston and raping his mistress Valerie Storie, then shooting her, leaving her paralysed. Gregston, 36, and Ms Storie, 22, were hijacked in their car off the A6 in Berkshire then attacked near Bedford. Hanratty, 25, denied the crime and his family battled for 40 years to clear him. His body was dug up in 2001 and DNA tests showed he was guilty.
