In 1983 and then, only three years later, in 1986, the villages of South Leicestershire were paralysed in fear by the disappearance and murder of two teenage girls. Both victims were only 15 years old and both were killed within one mile of each other. Meanwhile, 5 miles north of where these events were taking place, geneticist Sir Alec Jeffreys made the first DNA fingerprint, a technology that has since aided the capture of violent criminals and exonerated the innocent.
Thirty-six years ago, Lynda Mann set off home after babysitting. She chose to take a short-cut along a nearby footpath, locally called the Black Pad, but she did not return home. Her body was later found in the corner of a field near the footpath. Two and a half years later, Dawn Ashworth set off from a friend’s house in Narborough and headed home, but she also never made it home. Two days later, Dawn’s body was found a several hundred yards from the scene of Lynda’s murder. Both girls were killed in similar circumstances, so police quickly realised they were looking for a serial killer.
In 1984, Alex Jeffreys was pursuing ways to trace genes through family lineage, by utilising fragments of repeated DNA that show great variation in repeat numbers between people. He designed an experiment to see if he could determine the number of repeats an individual had in these regions. Briefly, DNA was removed from cells and cut using restriction enzymes, that act as molecular ‘scissors’. This process produces fragments of DNA that vary in length. These DNA pieces can then be separated by size using a process called gel electrophoresis. Radioactive probes are able to identify the repeated sections of DNA, and were added to the separated fragments and exposed to photographic film allowing for visualisation of the location of the probes. Jeffreys left the photographic film in the developing tank before heading home for the weekend. When he returned to the laboratory the next Monday morning, he removed the film from the tank and saw a sequence of bars had developed. He quickly spotted that the DNA of each person produced a different barcode, that could be used to identify them with great precision. When Jeffreys gave his first talk about this discovery, he suggested it could be used to aid criminal investigations. Some people in the audience laughed at such a suggestion.
After the discovery of Dawn’s body, Richard Buckland, a 17-year old with learning difficulties, admitted to the crime under questioning and was charged with Dawn’s murder. However, he was adamant that he was not guilty of murdering Lynda. After Buckland appeared in court, Jeffreys received a call from the police asking him if his discovery could prove that Buckland had also murdered Lynda. Jeffrey’s carried out DNA fingerprinting on the blood taken from both Lynda’s and Dawn’s body, as well as Buckland’s blood. As DNA fingerprints are unique to each person, it could clearly be seen that both girls were killed by the same person. However, the DNA fingerprint of the killer was not a match to the fingerprint of Buckland. The police were back to square one.
The following month, an operation to gather the DNA of every man in the surrounding villages was set up. After eight months over 5,000 men had given blood samples, marking this the first-ever mass DNA screening. However, there was no match. Colin Pitchfork, a local 27-year old, was recorded as having given a sample. In the summer of 1987, a man named Kelly loudly confessed to have taken the blood test on behalf of Pitchfork, while having a pint in the local pub. Another local overheard the conversation and reported it to a policeman. Later that day, Pitchfork was taken into custody and promptly gave a detailed confession to both murders. DNA testing later confirmed him as the killer of both Lynda and Dawn.
Although Jeffrey’s work was not tested by the court, due to Pitchfork’s guilty plea, the investigative potential of the technique was rapidly adopted by police forces around the globe. Since its discovery, it is estimated that more than 50 million people have had their DNA profiled in criminal investigations, ensuring the conviction of many criminals and proving the innocence of others.
(A little trivia about me, I grew up in the village where these events took place)