DNA fingerprinting enters society
12/02/04 by GN
Part
one of the DNA fingerprinting story examined its
discovery. In part two, Sir Alec Jeffreys explains its first
uses in immigration disputes and in criminology.
Immigration issues
When the first paper on DNA fingerprinting was published in
spring 1985, it was covered in the press – and one report
in the Guardian was read by Sheona York at the Hammersmith
and Fulham Community Law Centre. Her clients, a Ghanaian family
who were UK citizens living in London, were stuck in an immigration
dispute. The youngest son had travelled back to Ghana, but
on his return to the UK was detained due to an allegedly forged
passport – the question being whether the boy coming
back was in fact the son or was a substitute.
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Standard DNA fingerprints in an immigration dispute |
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"We took
the case on – and it was a tricky case," says
Professor Jeffreys. "The woman had sisters back in
Ghana, so the boy could have been a nephew, and we didn’t
have the father for analysis. All we had were three fully
accepted children – so we used these children to
reconstruct the DNA fingerprint of the missing father.
When you compared mum, dad, and the boy, the results were
clear-cut – the boy was definitely the son." |
The case against the son was dropped, and huge press coverage
ensued. "It was a good news story of ‘science fighting
bureaucracy and helping families’", says Professor
Jeffreys. The University of Leicester switchboards were soon
jammed with calls about immigration. "I didn’t realize
the scale of the problem, thousands of families were trapped
in exactly this sort of dispute," he adds. Indeed, DNA
fingerprinting led to a change in the Immigration Act.
Innocent or guilty?
Although the principle of DNA fingerprinting seemed ideal
for forensics, in practice the patterns would have been too
complicated to explain in court. A slightly tweaked approach
– termed DNA profiling – was the answer.
As Professor Jeffreys’s team uncovered more and more
minisatellites in the human genome, they were finding some
that were stupendously variable. DNA profiling therefore focused
on just a few of these highly variable minisatellites, making
the system more sensitive, more reproducible and amenable
to computer databasing.
In 1986, the Enderby murder case, a case local to Leicester,
saw the first use of DNA profiling in criminology. Two young
girls had been raped and murdered, one in 1983 and one in
1986. After the second murder, a young man was arrested and
gave a full confession. The police thought he must have committed
the first murder as well, so they asked Professor Jeffreys
to analyse forensic samples – semen from the first and
second victims, samples from the victims, and blood from the
prime suspect.
"The police were right – both girls had been raped
by the same man," says ProfessorJeffreys. "But it
wasn’t the man who had confessed. At first I thought
there was something wrong with the technology, but we and
the Home Office’s Forensic Science Service did additional
testing and it was clear that it was not his semen. He had
given a false confession and was released – so the first
time DNA profiling was used in criminology, it was to prove
innocence."
Armed with the DNA profile of the assailant, the police launched
the world’s first DNA-based manhunt. Blood samples from
more than 5000 men in the local community were collected.
The murderer nearly got away with it – sending a proxy
in to give a blood sample – but eventually he was apprehended
and got two life sentences. "This man would have killed
again, no doubt about it," says Professor Jeffreys. "
DNA testing helped to save lives."
Within a year, DNA profiling was being used around the world.
But the development of the technique was not finished. The
arrival of the polymerase chain reaction enabled another huge
leap in forensics: the development of national DNA databases.
In part three
of the DNA fingerprinting story, Sir Alec Jeffreys discusses
the introduction of PCR to DNA fingerprinting and the launch
of the National DNA database, and argues for a DNA database
for all citizens.
Further reading
Jeffreys A J, Wilson V and Thein S L (1985) Hypervariable
'minisatellite' regions in human DNA. Nature 314: 67-73.
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