Killer breakthrough – the day DNA evidence first nailed a murderer

It's 30 years since DNA fingerprinting was first used in a police investigation. The technique has since put millions of criminals behind bars - and it all began when one scientist stumbled on the idea in a failed experiment

Thirty years ago this summer, at 4.30 one Thursday afternoon, a 15-year-old schoolgirl called Dawn Ashworth set off from a friend's house in the village of Narborough, Leicestershire, and began to walk home. Dawn lived in the nearby village of Enderby, a few minutes' walk away, and chose to take a short-cut along a footpath known locally as Ten Pound Lane. And then she vanished. It was not until two days later that Dawn's body was found in the corner of a nearby field, covered in twigs, branches and torn-up nettles. The pathologist established that she had put up a considerable struggle before being raped and strangled.

The hunt for Dawn's killer was unlike any previous murder investigation, however: it was conducted with the help of a new science. The technique known as DNA fingerprinting was employed in a criminal investigation for the first time. Not only did this revolutionary technique lead, indirectly, to the killer being caught; it also prevented a grave miscarriage of justice. And it was employed in a manner that would, today, be likely to face resistance from some members of the public.