When was DNA fingerprinting first used and how does DNA profiling help in crime investigations?
A NEW series, Catching Britain’s Killers looks at three murders that changed the way investigations are conducted in the UK today.
The first episode focuses on Colin Pitchfork, the first person be convicted of murder using DNA fingerprinting. Here is more about the technique.
What is a DNA fingerprint?
DNA - or genetic - fingerprinting relies heavily on the principle that no two individuals share the same genetic code.
The technique was developed in the summer of 1984 by Alec Jeffreys, then a 34-year-old Leicester University genetics researcher.
He was looking for ways to trace genes through family lineages.
Dr Jeffreys discovered that repetitive patterns of DNA, known as Variable Number of Tandem Repeats were present in all human beings but that they varied in length for each individual.
He soon realised that this variation could be used to establish the identity of a person and he named his technique genetic fingerprinting.
He demonstrated that a genetic fingerprint is specific to each individual and the pattern does not belong to any other person on earth except for identical twins.
In 1994, Professor Jeffreys – as he became – was knighted for his work.
How does DNA profiling help in criminal investigations?
The use of DNA fingerprinting went on to transform forensic science and help to put many criminals who wouldn’t have otherwise been caught behind bars.
Its premise is that most attackers or killers will leave some measure of bodily fluid at a crime scene - be it saliva, blood, semen or other such fluid.
The technique was first used to crack two murders that took place in two towns in Leicestshire.
In 1983, 15-year-old Lynda Mann was found raped and murdered in Narborough and three years later, Dawn Ashworth, also fifteen, was also raped and murdered in Enderby.
Dr Jeffreys was asked to compare semen samples from both murders against a blood sample from 17-year-old year old suspect, Richard Buckland.
He was in police custody and who had confessed to the second crime but officers were sceptical that he was the culprit.
The DNA fingerprint from the semen found on the two murdered victims was not the same as Buckland's.
But it proved that the same killer was responsible for both crimes.
Investigators then embarked on the unprecedented of collecting DNA samples from a total of 4,582 men in three towns, to test for killer's blood type.
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Local baker Colin Pitchfork avoided having his blood tested and gave a colleague his passport in which he had replaced his picture with for that of the other man’s, who gave blood for him.
The deception was discovered by police when a resident came forward after hearing a conversation in a pub in the man admitted he was paid by Pitchfork to have his blood tested.
Pitchfork was arrested and Dr Jeffreys compared his DNA with the DNA of the semen found on the two victims which came out as a perfect match.
He pleaded guilty to both rapes and murders and was jailed for life in 1988.
- Catching Britain's Killers: The Crimes That Changed Us airs on October 9, on BBC Two at 9pm
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