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Update on DNA

NZ $40.00
This book is only available in PDF format
Author(s): His Honour Judge Arthur Tompkins, Murray Gibson, Simon Walsh
Published: 14 May, 2001
Pages: 90



In 1953 two young and slightly dishevelled men emerged from the Cavendish Laboratory in Bene’t St in Cambridge, England, crossed the road and entered the Eagle pub. Without, as it turned out, a trace of overstatement, one of them quietly announced to the assembled patrons that they had discovered the secret of life. Their names were Francis Crick and James Watson, and together they had discovered the structure of the deoxyribonucleic acid molecule. It was in the form of a double helix, somewhat akin to a twisted ladder. Two years later they received the Nobel Prize for their efforts, and their work is a compelling candidate for the description of the most important scientific discovery of the 20th century.

In England in the1980s, a scientist named Alec Jeffreys, working in Leicester with his assistant Vicky Wilson, received a request from local police. The body of Dawn Ashworth, a local schoolgirl, had been found in scrub near a village called Narborough. She had been raped and strangled. A local mentally retarded man named Buckland had confessed to the crime. But he refused to confess to the strikingly similar rape and killing of another schoolgirl, Lynda Mann, in the same area three years earlier. Jeffreys and Wilson had recently stumbled on, and then developed, the first DNA profiling technique, using a “hypervariable minisatellite array” found in the gene which codes for the human protein myoglobin. Police gave Jeffreys a blood sample from Buckland, and semen samples from Ashworth and Mann’s bodies, in an effort to prove that Buckland was indeed the killer of Mann as well.

Jeffreys found that both semen samples must have come from the same man. But that man was not Buckland: he could not be the murderer. Over the stunned protests of Police (they termed the result “bloody outrageous”), Jeffreys was steadfast. Buckland was released after spending 3½ months in custody. Some months later, a man named Colin Pitchfork persuaded a co-worker at a local bakery to take a blood test for him, the samples being given as part of the testing of 5,500 men in the Narborough area. The police were looking for a DNA match between the semen samples and the unknown murderer. Pitchfork told Kelly that the police were trying to frame him. In time police heard of the swap and located Pitchfork. In 1988, after confessing to both killings, Pitchfork was sentenced to life in prison.

It is 2003. A long series of unsolved violent sexual attacks throughout New Zealand is causing considerable unease. It is readily apparent that the same man is responsible for all the attacks. Numerous bodily samples have been recovered from victims, and the same man has been identified as the offender, but the police have been unable to identify him. No matching profile exists on the police DNA databank. They apply to the High Court for an order entitling them to have access to all blood and body samples held by hospitals and medical laboratories throughout New Zealand, including all records held as a result of cholesterol testing and the blood taken from all new-born babies, for the purpose of submitting those samples to DNA analysis in an effort to find the offender.

In the Family Court in mid-2005 a couple are disputing custody of their young child. Both parents are in their mid-twenties. Genome analysis shows that the mother has, on her fourth chromosome in a gene called the Wolf-Hirschhorn gene, fifty repetitions of a single “word”, CAG. If she had had fewer than thirty-five repeats of this same word, it would be irrelevant. But because she has those forty two repeats, she is doomed to a slow and horrific death. She will, at age thirty seven, experience the onset of dementia and loss of balance. This will be followed by jerking limbs, deep depression, occasional hallucinations and delusions, and, 15-25 years later, death. The course of this horrific and irreversible disease, called Huntington’s chorea, is inexorable and pre-determined from the moment of conception. The difference between those who will succumb and those who will not is infinitesimal, and solely the result of the difference in the number of repeats of the three base word CAG on the Wolf-Hirschhorn gene. How the mother lives her life, whether she eats well or badly, or smokes or abuses drugs, will have absolutely no effect. The father argues that because of that, he and not the mother should have custody of the child.

The first two situations described above are historical. The final two are speculative, but not unrealistic.

This seminar is about DNA, its use within the justice system, and some of the questions it raises.

The two speculative situations sketched above raise the kinds of issues which have started and will continue in various forms, to come before the courts as technology improves, and DNA testing becomes cheaper, faster and more ubiquitous. The justice system will have to confront and resolve these and other collisions of interests involved.

Many lawyers became lawyers because science and mathematics held no appeal, or caused them heartache and struggle during their schooling. But inevitably, science will intrude more and more into the courtroom, as Justice Stephen Breyer of the US Supreme Court has noted:

In this age of science, science should expect to find a warm welcome, perhaps a permanent home, in our courtrooms. The legal disputes before us increasingly involve the principles and tools of science. Proper resolution of those disputes matters not just to the litigants, but also to the general public – those who live in our technologically complex society and whom the law must serve. Our decisions should reflect a proper scientific and technical understanding so that the law can respond to the needs of the public.

Although Watson and Crick described the DNA molecule’s shape, they did not at that time attempt to describe or map the actual structure of the molecule. That is hardly surprising. There are some 3 billion or so base pairs, making up approximately 30,000 genes, situated on the 23 pairs of chromosomes contained in, with a few exceptions, every human cell. The mapping of the human genome was an enormous undertaking which reached its first major milestone late last year when 95% of the base pairs which make up the human genome were, somewhat ahead of schedule, finally mapped, principally by the publicly funded Human Genome Project and the privately funded Celera Corporation, involving sixteen nations and costing upwards of US$3 billion. The Times described the breakthrough thus:
Imagine that you are exploring a gigantic underground cavern whose walls are covered with three billion extraordinarily detailed drawings and alphabetic squiggles that are thought, if you could only see them perfectly, to hold the secret of life itself. With only matches to light your way, you have spent decades trying to copy just a few of these drawings. Now, suddenly, the entire expanse is illuminated by brilliant searchlights that leave no corner, no crack in darkness. That is what will happen on Monday, when scientists on both sides of the Atlantic formally present the first “working draft” of the entire human genome.

Although the mapping of the genome was a vast undertaking, the differences between individual human beings are surprisingly tiny, and those between humans and other mammals and animals are likewise small:
For all the diversity of the world’s five and a half billion people, full of creativity and contradictions, the machinery of every human mind and body is built and run with fewer than 100,000 kinds of protein molecules. And for each of these proteins, we can imagine a single corresponding gene (though there is sometimes some redundancy) whose job it is to ensure an adequate and timely supply.
In a material sense, then, all of the subtlety of our species, all of our art and science, is ultimately accounted for by a surprisingly small set of discrete genetic instructions.
More surprisingly still, the differences between two unrelated individuals, between the man next door and Mozart, may reflect a mere handful of differences in their genomic recipes – perhaps one altered word in five hundred. We are far more alike than we are different. At the same time, there is room for near-infinite variety. It is no overstatement to say that to decode our 100,000 genes in some fundamental way would be an epochal step toward unravelling the manifold mysteries of life.

DNA is fast becoming commonplace in the media. Seldom does a week pass in New Zealand without some reference to it. Issues of funding, privacy, and the potential for errors have all been accorded a high profile in recent years.

Contents outline

  • The basic science of DNA
  • DNA in the courts
  • Practical applications
  • The Future
    • Post-conviction exoneration
    • A case for review
    • New technologies and future directions
View contents page

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