False DNA matches could be likely

Wednesday, February 03, 2010

The man who invented techniques for DNA fingerprinting has warned that the likelihood of a false match on the DNA database could be increasingly likely, writes Mike Lowe.

Sir Alec Jeffreys was asked by the Home Affairs Select Committee whether he recognised the Home Office figures of a one in a billion chance of a false match on the national DNA database. He replied: "I recognise it as a rather gross approximation.

"The chance that your DNA, using current profiling systems, would match mine is to the order of one part in 10 trillion. One in a billion is a more conservative figure used in courts. That in a way is a rather meaningless number."

Sir Alec explained that the odds of a false match are about a million times less likely than winning the national lottery. But, he added, someone wins the national lottery every week.

"Now if we look at the lottery of the DNA database, you have five million players in there and you're running the lottery tens of thousands of times a year by doing searches across it. So even matches down to the one in a trillion level actually start becoming likely," he said.

"More seriously it's close relatives. So that one in 10 trillion changes to about one in 200,000 for brothers and there are certainly many, many instances where a pair of brothers are on that database."

Sir Alec said he has a "very major concern" that a false convinction could occur. The damage that could do to the public perception of the DNA database could be very serious indeed, he told the committee.

The DNA pioneer admitted that he objected profoundly to his own DNA being stored on the database, adding that DNA is a highly intimate sample that holds a lot of very personal information.

Thus Sir Alec said he had real "fundamental concerns" over the government's six year retention plans for anyone suspected of a crime.

"I'm not a lawyer but I always understood that one of the great foundations of English law was a presumption of innocence. What we're seeing now is a presumption of future-possible-guiltyish-ness, but currently you may be innocent-ish. I find that a deeply worrying shift in the whole ethos of how the legal system operates," he concluded.

Policing minister David Hanson gave his full backing to the scheme, telling the committee: "The government position remains that we believe that a six year period is appropriate and proportionate."