It will be 25 years on Thursday since British scientist Professor Sir Alec Jeffreys discovered the DNA fingerprint. Claire Marshall joined him in his laboratory to talk about his breakthrough and the changes it has wrought over the last 25 years.
Professor Sir Alec Jeffreys still works in the same laboratory at Leicester University where, a quarter of a century ago, he discovered, by chance, the genetic fingerprint.
His "eureka" moment came on the morning of Monday 10 September 1984 when he pulled an x-ray film out of the developing tank in the laboratory.
DNA fingerprint inventor shocked by impact of discovery
He could see patterns in the genetic material which completely discriminated between the three people who had been involved in the analysis: a technician, and a mother and a father.
"Within seconds," said Prof Jeffreys, "it was obvious that we had stumbled upon a DNA-based method not only for biological identification, but also for sorting out family relationships. It really was an extraordinary moment."
The new technique quickly attracted publicity when it helped to settle a difficult immigration case.
Leicestershire Police then contacted Prof Jeffreys, asking for his help in solving a double murder. In 1986, 15-year-old Dawn Ashworth, was brutally raped and murdered in the village of Enderby.
I took it on with a considerable degree of foreboding. No-one had ever attempted a crime scene DNA analysis before
Professor Sir Alec Jeffreys
Three years earlier another 15-year-old, Linda Mann, had been murdered in a neighbouring village.
A local youth, Richard Buckland, had confessed to Dawn's killing, but with no corroborative evidence, the police could not prove he was the murderer. In desperation they turned to Prof Jeffreys.
"I took it on with a considerable degree of foreboding," Prof Jeffreys said of the case. "No-one had ever attempted a crime scene DNA analysis before."
He described the moment when the "intimate samples" of the victims were given to him as a "chilling moment".
Prof Jeffreys ran a test against blood samples taken from Mr Buckland.
The tests delivered surprising results.
"We took on the analysis in full expectation we would get nothing back at all. But we got - I confess to my astonishment - a completely clear readout, which was that one of the suspects who had confessed to the murders was not guilty of that crime."
The analysis proved that both girls had been killed by the same man - but that that man could not be Richard Buckland.
In a surprise twist, Mr Buckland had just become the first person to be exonerated using DNA profiling.
The police realised that to catch their killer they would have to cast their net far wider, and in a test which would change forensic science forever they collected blood and saliva samples from 5,000 men.
Colin Pitchfork confessed when presented with the DNA evidence
Within a year, despite an attempt to evade screening, local baker Colin Pitchfork became the first person convicted of murder in Britain using DNA evidence, and was sentenced to life imprisonment.
However, as Prof Jeffreys explained, although DNA profiling had proved its worth, it could not yet be widely used due to the rudimentary testing techniques.
"It took a lot of DNA, and a lot of effort to get a result from a DNA sample. The real problem was that in most crime scene samples, you knew that human DNA was in there - you just didn't have a technology sensitive enough to type it."
A breakthrough technological development in the late 1980s enabled scientists to get a profile from the tiniest amounts of DNA.
Prof Jeffreys was able to identify the exhumed remains of the Auschwitz Angel of Death, Josef Mengele, who fled Germany after the end of World War II.
"The sheer power of DNA amplification meant it was possible to get a read out from less than a thousandth part of a millionth part of a gram of DNA... we got a read out and compared them to DNA of Mengele's wife and son who were living in Germany."
Gathering DNA evidence has now become routine practice in most UK criminal investigations.
DNA fingerprint inventor on database fears
Samples are tested and stored by the Forensic Science Service. The combined British database now holds the profiles of more than five million people.
In Scotland, the DNA of most of those arrested but not convicted is later deleted.
But profiles gathered in England and Wales, are kept indefinitely.
Last December, the European Court ruled that this was illegal, but the government has yet to change the law. This, said Prof Jeffreys, is unacceptable.
"We now have a database which is populated with in the order of eight hundred thousand entirely innocent people. This does raise very serious issues of discrimination - breach of genetic privacy, stigmatisation - a whole host of issues," he explained.
"My view is very simple... innocent people do not belong on the database. Branding them as future criminals is not a proportionate response in the fight against crime.
"I've met a fair number of these people, and these people are very, very upset, they are distressed, by the fact that their DNA is on the database, they cannot get it off, and they feel as if they're branded as criminals."
However, as DNA profiling ceases to be the sole province of the police, Prof Jeffreys said he has other concerns too.
"I have seen television programmes where DNA results of a paternity test were revealed to the participants as entertainment, which I think is a complete outrage.
"This is very important testing which can be life-changing for a family, and it should be done in the correct context, of counselling of those individuals."
Prof Jeffreys said he is also concerned about DNA database security.
"Before long you will be able to send off a mouth swab and get your entire genome, all 3,000 million bases, with millions of sites of variation, typed - what the final cost will be and when this will happen I don't know, but the technology is rapidly moving towards that potential.
"There are big issues of regulation here. So if, for example, you sent off your DNA for complete genome sequence, with every single type of variation in there, what legislation covers the retention of that highly personal information - will it held by the company?
"What are their safeguards? How will it be used? If you have it, what are you going to do with the information?"
However, when asked if the mission creep of DNA profiling which he has seen over the last 25 years meant that overall his discovery had not been good he disagreed.
"The benefits? Catching large numbers of criminals, exonerating the innocent - these are people, some of whom have spent more than 30 years in jail, immigrant families reunited... I would argue the good heavily outweighs the bad," he said.
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