Breakthrough in DNA tests key to solving more murders

All British police forces have been asked to re-examine their unsolved murder and rape inquiries in the light of new DNA testing techniques, which have been used to re-open the Barbara Mayo case in Derbyshire.

The Forensic Science Service has traced a DNA profile from minute body samples found on the clothes of the student teacher, who was strangled 27 years ago.

With 838 unsolved murders since 1975 lying in police files, the Mayo case's success has prompted reviews of other incomplete investigations. Forces are being encouraged to act by the DNA Users' Group, representing the FSS and the Association of Chief Police Officers.

The Police Superintendents Association said that such a review "could pay dividends" in forces with diligent crime departments who had preserved old forensic evidence.

Spokesman Supt Gwyn Lewis said: "In the majority of murder cases by non- family members, the victim fights back, hair gets pulled out and there can be blood. It's difficult to have a struggle and not leave evidence behind."

The techniques enable DNA, the molecular building block of life, to be identified from material that is degraded and small, such as hair, nails and faeces.

"It would be good practice for forces to revisit cases of their serious outstanding offences to see if there is any evidence for conversion to DNA," said Ben Gunn, Chief Constable of Cambridgeshire and ACPO crime committee spokesman on forensic science. He added that clothes collected from murder scenes would provide the best hope, which could contain hair or bloodstains from an attacker.

The Mayo inquiry could be widened if tests can be carried out by Cheshire police on the body of another hitch-hiker, Jackie Ansell-Lamb, an 18-year- old secretary who was killed the same year. She was also raped, strangled and dumped near another motorway, this time the M6.

A Derbyshire police spokesman said: "Should a test be successful and find matching DNA, we would have a serial killer investigation that would get huge."

Hampshire police have sent forensic scientists a fingernail clipping of Helen Gorrie, a 15-year-old whose strangled and partially-naked body was discovered in bushes by wedding guests attending a reception at a community centre in the village of Horndean in 1992.

Det Insp Colin Smith said the inquiry was "progressing", but would not discuss whether the tests would lead to arrests.

The advances in technology led to the setting up of a National DNA Database at the Forensic Science Service in Birmingham in 1995, which now holds more than 180,000 samples. It allows forensic scientists to check DNA samples taken from the scenes of crimes and see whether they match samples held on computer of known and suspected criminals.

Arrested, charged or reported suspects are compulsorily swabbed for a sample and this too is sent to the database, to see if it matches any DNA found at the scene of different crimes.

The database will become 20 million times more accurate this year, because of changes introduced by the Forensic Science Service. This will make it almost impossible for matches to be made in error. Only one case in 1,000 million million is expected to be faulty. Six elements of DNA are tested under the existing system, giving an accuracy ratio of 50 million to one. The new test will cross-refer twice as many elements.

Police forces have increasingly been using DNA techniques. Since April this year there have been 3,637 matches involving burglaries, 468 for vehicle crime, 24 for rape and 10 for murder and manslaughter.

One-third of checks now reveal matches, which compares with an average of 10-12 per cent for fingerprinting. Cases that have been bought to trial through the tests are reaching the courts in increasing numbers.

The more accurate testing has been welcomed by DCI Doug Smith, head of the National Crime Faculty. He said: "The more specific we can be the better. The more reliable DNA evidence is, the more courts will accept it."