At about nine o'clock on the morning of Monday 10 September 1984, a geneticist named Alec Jeffreys pulled a strip of X-ray film out of a developing tank in his laboratory at the University of Leicester and stopped dead. He was not looking for a revolution. He had been studying how a particular gene varied between people and had developed a technique that produced, on the film, a ladder of dark bands rather like a supermarket barcode. What struck him was that the pattern was wildly different from one person to the next — and yet the bands a child carried could be traced, some to the mother and some to the father. In a single glance he understood that he was looking at a way to identify any individual, and to prove who was related to whom, from a smear of blood or a fleck of tissue. He later said the penny dropped in his mind in seconds; within half an hour his team were already talking about paternity tests and catching criminals.
Reading the repeats
The trick lay in stretches of DNA that repeat over and over, which Jeffreys called minisatellites. The number of repeats at each site varies enormously between people, and the combined pattern across many sites is, for practical purposes, unique to each person, identical twins aside. Jeffreys named the technique DNA fingerprinting, and its first real-world use was not a murder at all but an immigration dispute: he used it to prove that a Ghanaian-British boy, whom the authorities suspected of being an impostor, was genuinely the son of the woman claiming him, allowing him to stay in Britain. Families and courts had never had such a tool.
Then came the crime that made it famous. In the villages of Narborough and Enderby, near Leicester, two teenage girls had been raped and murdered three years apart — Lynda Mann in 1983 and Dawn Ashworth in 1986 — in strikingly similar attacks. Police had a suspect for the second killing, a local youth named Richard Buckland who had confessed to it. They asked Jeffreys to use his new method to tie Buckland to the first murder as well.
The technique that freed a man and caught a killer
The DNA told an unexpected story. It confirmed that the same man had committed both murders — but it also proved that man was not Richard Buckland. In the first use of DNA evidence in a criminal case anywhere in the world, the technique exonerated the prime suspect, who might otherwise have been convicted on his false confession. The real killer was still free.
To find him, police launched the first mass DNA screening in history, asking thousands of local men — some five thousand in all — to give blood or saliva voluntarily so their profiles could be checked against the crime samples. Month after month, no match came. Then, in a pub, a woman overheard a man boasting that he had been paid to give a sample in someone else's name. A baker named Colin Pitchfork, it emerged, had persuaded a colleague, Ian Kelly, to take the test for him, doctoring a passport photo so Kelly could pose as Pitchfork. When the story reached the police, Pitchfork was arrested, his own blood was tested, and it matched both murders exactly. In 1988 he became the first person in the world convicted of murder on the basis of DNA evidence.
The implications rippled far beyond one English county. DNA profiling swiftly became the gold standard of forensic identification, transforming criminal justice around the globe. It has convicted the guilty on the strength of a single hair or a licked stamp, and it has freed the innocent: through projects that re-examine old cases, DNA evidence has overturned hundreds of wrongful convictions, some of them of people who had spent decades in prison or sat on death row. Its power to establish parentage rewrote family law, and its ability to trace ancestry launched a whole industry of genetic genealogy — the same techniques that, decades later, would help identify long-cold serial killers from the DNA of their distant cousins.
For all that, the founding lesson of the field was written in Leicester in the 1980s, and it cuts both ways. The very first criminal use of DNA fingerprinting did not put a man behind bars — it took a false confession apart and set an innocent suspect free, before turning its gaze, unerringly, on the man who had done it.
Quiz nuggets
- Alec Jeffreys discovered DNA fingerprinting at the University of Leicester on 10 September 1984.
- The technique reads highly variable repeating stretches of DNA called minisatellites, producing a pattern nearly unique to each person.
- Its first criminal use exonerated suspect Richard Buckland before identifying the true killer.
- Colin Pitchfork, who had a colleague named Ian Kelly take the test in his place, became the first person convicted of murder using DNA evidence, in 1988.
- The case, involving the murders of Lynda Mann and Dawn Ashworth near Leicester, also featured the first mass DNA screening, of around 5,000 men.