Revealing who killed 18-year-old Rita Sawyer would cause unnecessary suffering to the murderer's family, officers fear.

Rita's partially-clothed body was found in a field near the village of Chesterton, Warwickshire, in September 1970.

A post-mortem examination revealed that the dead girl, who was three months pregnant, had been stabbed repeatedly.

Took secret to grave

Detectives said the man responsible died last year from natural causes.

He was local to the area of the crime, but had not been a suspect in the original inquiry.

DNA was the key which unlocked the murder mystery

The case was reopened in May, when Warwickshire police announced that advances in DNA profiling had resulted in a genetic fingerprint of the killer being obtained.

At the force's headquarters in Leek Wootton, Det Insp Gino Varriale, who headed the new inquiry, told a press conference a sample taken by officers in the course of the re-investigation had been matched to semen stains left by the killer.

"The Forensic Science Service over recent months has been working on samples we have submitted, and I am able to tell you today that a DNA profile developed from one of those samples matched our profile," he said.

"The man who has been identified died last year, and quite obviously there will be no further proceedings."

He said the man, who was from Leamington Spa, would have been in his late 20s at the time of the murder.

"He was spoken to in the course of the investigation but he did not feature with any degree of prominence."

At the time of the original inquiry, some 10,000 people were interviewed and 2,600 witness statements were taken.

"The original investigation was thorough and detailed and it is purely through advances in investigative techniques, forensic science and information technology that we have been able to resolve this case after 29 years," said Det Insp Varriale.

"The nature of the evidence is such that we are not looking for any other person in connection with this murder and the file will be closed."

Protect family

The decision to protect the identity of the killer was taken out of compassion for his family, officers said.

Det Supt Steve Hussey told reporters: "The man who murdered Rita Sawyer 29 years ago leaves behind him a partner, children who are now fully grown and siblings, who were not aware of his involvement in this crime.

"It would be unfair on these people to publicly denounce the man so many years later, particularly given the fact that we now know that they too suffered traumatic experiences at his hands.

"For reasons of compassion therefore we shall not be disclosing his identity. I can also say the murderer was in no way connected to Rita Sawyer's family and to disclose his identity would serve no useful purpose."

The officer said the family of the murdered girl had not been told the killer's identity and understood the reasons for anonymity.

Det Insp Varriale said: "The family of Rita Sawyer have asked me to say that they are extremely pleased and relieved and this will help them to draw a line under what is a sad episode in their lives."

He refused to comment on how the murderer's DNA had been obtained.