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Thursday, Aug. 8, 2002
DNA testing for all?
By ROWAN HOOPER
The 1986 rape and murder of a 15-year-old schoolgirl in an otherwise quiet village in central England did more than shock residents: It led to the worldwide acceptance of what Australian scientists Robert Williamson and Rony Duncan call in this week's Nature "the most important advance in forensics in our generation, and probably in human history."
Three years earlier, another girl had been abducted from a country lane as she walked home from school. She was also raped and murdered, and similarities between the two killings led police to believe that one man was responsible for both. A kitchen porter was arrested, and he confessed to the second murder but denied knowledge of the first. The police needed some way of implicating him in the first case.
So they sent a blood sample from the kitchen porter and forensic samples from the victims' bodies to Alec Jeffreys, a molecular biologist at nearby Leicester University. The year before, Jeffreys had discovered that all humans (apart from identical twins) have a unique DNA sequence, like a fingerprint, and on this basis he analyzed the samples the police had sent him.
He found that the police were right in their supposition that one man had killed both girls. However, despite the confession, the killer was not the porter. His confession to the police had been false, and the man was released -- the first time that a suspect had been proved innocent by the technique now known as DNA fingerprinting.
But the elimination of a suspect is just one of the two aspects of DNA testing. Next, the other came into play -- the linking of a suspect to a crime.
With the DNA fingerprint of the rapist/murderer, the police commenced the world's first DNA manhunt. All men in the area between 18 and 35 were asked to provide blood samples, and more than 5,000 complied. The criminal, Colin Pitchfork, tried to evade the police by getting his friend to give blood in his name, but the friend was overheard talking about it in a pub and Pitchfork was arrested. His blood was tested and his DNA found to match the samples taken from the two murdered girls. In 1988, Pitchfork was convicted and is currently serving two life sentences.
While DNA fingerprinting is now routinely used all over the world and methods of DNA recovery have become far more sophisticated, that first case encapsulates everything that is useful about the technology -- and everything about it that worries civil liberties campaigners.
A DNA sample is "the ultimate form of evidence," say Williamson and Duncan, of Murdoch Children's Research Institute at the University of Melbourne. DNA fingerprinting has been used to establish the guilt -- and the innocence -- of thousands of suspects. But can the giving of DNA samples really be called "voluntary" when not doing so would arouse suspicion? And could samples be misused? How should we go about DNA testing? According to Williamson and Duncan, everyone should be tested -- at birth.
"It is in society's interest that those who commit serious crimes are identified and convicted, but this can only be accomplished if society is convinced its civil liberties are not at risk," Williamson said in an e-mail interview. "Therefore, we propose that no DNA samples are kept . . . and that the database should not be held by the police, but by an independent body."
If the DNA is kept, the information it contains is vulnerable to misuse, say by insurance companies who might want to know whether a client carries a gene for heart disease. One of the safeguards Williamson and Duncan put forward in their commentary in Nature is that the DNA sample be destroyed after testing, and the profile alone be retained by police. But contrary to expectations, even that may not be enough. A study published in 2000 shows that DNA fingerprints alone contain information about a person's susceptibility to type 1 diabetes.
DNA fingerprints are not patterns of a person's genes, they are patterns made by specific "markers," bits of "junk" DNA with no specific function that vary in length from person to person. Despite this, John Stead and colleagues from the University of Leicester found that one of the markers used in standard DNA testing is located close to the gene for insulin, and the size of the marker can indicate whether a person has a reliable or risky form of the insulin gene.
Team member Alec Jeffreys, the discoverer of DNA fingerprinting, said last year, "This marker is weakly linked to a shift in your predisposition to diabetes and the police should not be collecting that sort of information."
Williamson agreed with Stead and Jeffreys. "Only 'meaningless' DNA sequences should be used for forensic identification. No research should be done on these samples and no sequence that could be related to medical risk, or physical appearance, should be permitted to be used.
"We argue that it is possible to have a safe and fair system that should not alarm the whole community . . . I think that the community has a right to use powerful methods to detect violent criminals, such as the use of DNA identity tools, but it is just because these methods are so powerful that we need good protections of civil liberties in place. Yes, it is possible to do this, but it must be done in a sound legal way and be enforced by the justice system."
Since the advent of DNA fingerprinting, it has often been said that if Sherlock Holmes were alive today, he'd be a molecular biologist. The cops in that English village didn't know it back then, but Jeffreys' method effectively turned them -- and all criminal investigators in the world -- into supersleuth Sherlocks. What Williamson and Duncan want to ensure is that the bad guys, the Moriartys, don't misuse the technology.
Rowan Hooper can be contacted at email@example.com See more from Nature at www.nature.com