It says a lot about Sir Alec Jeffreys that his selection of Desert Island Discs included Engelbert Humperdinck's Release Me.

The scientist whose Eureka moment back in 1984 led to the discovery of DNA fingerprinting may have spent the last 30 years or so in a laboratory, but he's always been at pains to blow the dust off the often fusty world of academia.

Armed with no shortage of anecdotes on everything from the analysis of Monica Lewinsky's famous blue dress to how his discovery sadly disproved a long held myth his family were descended from George "Hanging Judge" Jeffreys, who once sentenced 300 men to death in one day, Sir Alec is committed to making the complex world of genetics accessible to the public.

Most of the time, he is happy to wax lyrical about the many successes of DNA fingerprinting and the thousands of criminals it has helped bring to justice, but more recently concerns have been growing about the expansion of the database.

When it was first set up, the database held only DNA samples from convicted criminals. However, a relaxation of the rules meant details of those arrested and later released without charge could also be held and a major inquiry is now underway after claims ethnic minorities have been disproportionately targeted.

This weekend saw further furore when Gary Pugh, who is due to become the Association of Chief Police Officers' spokesman on DNA, suggested that there was a preventative argument for fingerprinting young people who show signs of becoming criminals in later life.

"I have heard a third of all young black males are on it and that doesn't seem right," says Sir Alec, speaking at a University of Sheffield event. "I'm convinced that like every other country which has a database we should only be keeping the DNA of those who have been convicted of crimes.

"There has been talk of setting up a national DNA database where people would be registered at birth, but there are serious civil liberty issues.

"I do think there is an argument for a separate database which police wouldn't have access to and where the information was encrypted. We saw just how useful that could be after tragedies like the tsunami or 9/11 when the authorities were faced with hundreds of body parts which they were unable to identify."

Given the recent loss of 25 million child benefit details, trusting the Government with the entire country's DNA is bound to be controversial. However, the fact it is even being discussed shows just how far DNA fingerprinting has come since Sir Alec was in the labs of the University of Leicester at 9.05am on September 10, 1984.

"In those early days you wouldn't have hung a dog on the quality of the DNA fingerprints we were able to produce, but within a few months we were getting much richer patterns," he says. "The most sensible thing I did was to call it DNA fingerprinting, if we'd given it a more technical or scientific name I'm sure it would have taken much longer for anyone to take any notice.

"The following year a lawyer read a piece on our research and contacted us because he thought we might be able to help with an immigration case. The son of a family living in London had gone back to Ghana and when he tried to return 10 years later his British passport had expired and the authorities were convinced that another family member was trying to get in under his name.

"Through his DNA analysis we proved that he was telling the truth and to this day it is my proudest case."

What Sir Alec describes as a typhoon of paternity and immigration cases followed, but when two young schoolgirls were murdered three years apart in the small town of Narborough, in Leicestershire, its use in criminal cases quickly became apparent.

A sample of semen had been taken from the body of 15-year-old Lynda Mann in 1983, but, with no other evidence the murder hunt was eventually wound down. However, when Dawn Ashworth, also 15, was found strangled and sexually assaulted in the same town in 1986, the case was reopened.

"Police arrested a man who admitted to the second murder but denied the first," says Sir Alec. "They were convinced he was lying and called us in to see if we could prove he was responsible for both killings. As it turned out, the same man had been responsible, but it wasn't the person they had in custody, for some reason he had confessed to a crime he didn't commit.

"The thing about DNA fingerprinting is that it's not always about proving guilt, it's also about proving innocence. I'm convinced that without DNA fingerprinting an innocent young man would have been convicted and would have gone to jail for the rest of his life."

The case led to the launch of the first DNA manhunt and eventually the arrest of Colin Pitchfork and is now a staple of criminal proceedings. Steve Wright, the Ipswich prostitute killer, was caught because he had been convicted of a minor offence five years earlier and Sheffield rapist James Lloyd, who kept the shoes of his victims as macabre trophies, was traced after a genetic search linked evidence left at crime scenes with his sister, whose details were on the database following a conviction for drink-driving.

As DNA fingerprinting took on a life of its own, Sir Alec was knighted in 1994 and could have easily rested on his laurels. However, he remains a scientist at heart and his natural home is still the University of Leicester lab where he continues to conduct his own experiments.

"There are so many different avenues to pursue," he says. "The idea of being able to tell someone's physical appearance from their DNA is slowly coming along. It's already pretty good at identifying red hair and skin pigmentation, and interestingly ear wax consistency, although as yet I haven't thought of any particular use for that gem of information.

"The one thing you can't tell is age, so even if you could get a physical profile, if you don't know whether they are 19 or 90 it's not of massively great use."

With flaws in an individual's genetic make-up responsible for pretty much every disease you can think of, many believe DNA fingerprinting will become an increasingly valuable diagnostic tool.

It's not something Sir Alec disputes, but he does wonder whether when it comes to telling someone they will develop untreatable Huntingdon's disease or Alzheimer's a little information could be a dangerous thing.

"Certainly if you are able to screen women who for example have a history of breast cancer in their family, then it could potentially save lives or at the very least give people options to think about," he says. "However, when it comes to incurable diseases all you're going to do is scare them senseless. Who wants to live their life wondering when they are going to wake up with symptoms which they know can't be treated?

"Similarly, I really don't know how helpful it would be to identifying people carrying the so called obesity gene. It certainly does exist, but most people who are overweight also eat too much and don't do enough exercise. A DNA fingerprint won't change their lifestyle.

"I have no doubt that 20 years from now you will be able to go into a shop in the middle of Sheffield, hand over £250 and get your whole sequence of DNA analysed. The point is that most of us will die from a genetic flaw, me, I don't really want to know."

While Sir Alec has achieved more than most in his career, at 57 he is conscious that time is running out for him to find what he calls the Holy Grail of DNA fingerprinting.

"At the moment it takes around two hours to do a DNA fingerprint, what I'd really like to discover is how to do it in an instant," he says. "It would have massive implications in terms of registering people coming into the country and in terms of anti-terrorism.

"I'm aware the date is fast looming, but I'd really like to do it before I retire."

Only a fool would bet against Sir Alec achieving his dream.


BRITAIN'S DNA DATABASE


Britain holds DNA profiles on a higher proportion of its population than any other country, with one in 14 UK citizens and samples from 380,000 unsolved crime scenes on the database.

Since 2004, the data of everyone arrested for a recordable offence, all but the most minor offences, has remained on the system regardless of their age, the seriousness of their alleged offence, and whether or not they were prosecuted.

The national DNA database, which covers England and Wales, (Scotland has a separate database) has been in existence since 1995.

By the end of 2005, 200,000 samples which would have been destroyed before 2001 were retained.