Gripping story of when DNA helped to catch a killer for the first time

THIS new series looks back at some of the most important murder investigations ever carried out in Britain, in terms of the impact they had on the criminal justice system and our society as a whole.

Each of the tragic cases featured throughout the three-part series went on to revolutionise policing: whether by overturning outdated laws, transforming methods of police interrogation, or – in this first episode – creating extraordinary forensic breakthroughs.

The series begins with the murders of two teenage schoolgirls in Leicestershire in the 1980s. Lynda Mann was brutally raped and killed in the village of Narborough in 1983, and three years later the body of Dawn Ashworth was found in Enderby, less than a mile away.

The investigations were led by local detective David Baker, and had involved thousands of interviews and pieces of evidence, but the police could not find their man – and forensic intelligence was limited to things such as being able to identify blood group.

But Detective Baker had read that scientists at Leicester University were working on DNA identification, and approached them about the case.

Researcher Alec Jeffreys had stumbled on a way to visually represent a person’s DNA fingerprint, to show the unique genetic markers that could identify an individual, and his experimental tests were able to prove both girls had been attacked by the same man.

Trusting in the science, Baker ordered local men to give blood samples so their DNA could be tested – work which completely transformed the way crimes are investigated.

Professor Sir Alec Jeffreys, who invented DNA fingerprinting, which was first used to solve the murders of Lynda Mann and Dawn Ashworth Retired Detective Chief Superintendent David Baker of Leicestershire Police, who headed the investigation into the murders of Lynda and Dawn