The 1986 rape and murder of a 15-year-old schoolgirl in an otherwise quiet village in central England did more than shock residents: It led to the worldwide acceptance of what Australian scientists Robert Williamson and Rony Duncan call in this week's Nature "the most important advance in forensics in our generation, and probably in human history."
Three years earlier, another girl had been abducted from a country lane as she walked home from school. She was also raped and murdered, and similarities between the two killings led police to believe that one man was responsible for both. A kitchen porter was arrested, and he confessed to the second murder but denied knowledge of the first. The police needed some way of implicating him in the first case.
So they sent a blood sample from the kitchen porter and forensic samples from the victims' bodies to Alec Jeffreys, a molecular biologist at nearby Leicester University. The year before, Jeffreys had discovered that all humans (apart from identical twins) have a unique DNA sequence, like a fingerprint, and on this basis he analyzed the samples the police had sent him.