How Colin Pitchfork was first murderer convicted using DNA fingerprinting after killing two girls

The world's first murderer who was convicted using DNA profiling was in Enderby, in Leicestershire, between 1986 and 1988.

It was the investigation into the rape and murder of two schoolgirls - Linda Mann in 1983, and Dawn Ashworth in 1986.

Colin Pitchfork was found guilty of raping and murdering the two 15-year-olds from Leicestershire - and he was the first person in the world to be convicted using DNA fingerprinting technology - which was discovered not long before at the University of Leicester.

• How was Colin Pitchfork caught?

The prime suspect in the double rape and murder investigation was a boy named Richard Buckland.

He confessed to Dawn Ashworth's murder, but not to the murder of Linda Mann.

Police decided to use DNA profiling, thinking it would prove him guilty of both cases.

But when Buckland's DNA didn't match the killer's DNA, police launched a manhunt and blood samples of 5,000 local men were taken.

Buckland became the first suspect cleared using DNA profiling.

The actual killer, Colin Pitchfork, asked a friend to provide a blood sample on his behalf during the testing.

He was finally caught after the cover-up was realised.

Pitchfork's DNA matched that of the killer and he was sentenced to life imprisonment in 1988.

What is DNA profiling?

DNA profiling is also known as DNA fingerprinting.

It's where minisatellites - short sequences of chemical building blocks in DNA - are tested one at a time to give a pattern completely unique to a particular person.

DNA itself only shows slight variation from one person to the next, so testing minisatellites which are completely unique makes it ideal for forensic identification.

• How did DNA profiling happen?

In the 19th century, DNA was first discovered by Swiss chemist Friedrich Miescher, from pus on bandages.

By the 1940s, scientists realised that DNA contained the code for life and then discovered how genetic information was stored in DNA and transferred to the next generation.

In 1984, Alec Jeffreys discovered the variations in DNA, unique to each individual.

He discovered the technique of genetic fingerprinting, or genetic profiling, in a laboratory in the Department of Genetics at the University of Leicester.

Speaking on genetic profiling, Professor Sir Alec Jeffreys said: "It does not solve crimes. It establishes whether sample X comes from person Y. It is then up to the court to interpret that in the context of other evidence in a criminal case."

When Pitchfork was convicted, Jeffreys said: "I felt relief because he was a serial murderer and would kill again, and because if the operation had failed then the public's perception of forensic DNA would have been shattered.

"Also, here was a serial killer in the region who knew what I was doing and where I worked and where my family lived.

"That feels very uncomfortable so on a personal level it was a great relief when he was trapped."

The original DNA profiling technology used to catch Pitchfork is now largely obsolete.

The techniques have been speeded up and simplified.

In the UK there is a national database of 2.5 million genetic profiles from convicted criminals - which the police say is one of the most powerful tools in their fight against crime.

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