The trusted system that wrongly fingered a detective

When fingerprint experts told Detective Constable Shirley McKie that her thumbprint had been found at the scene of a murder, she said it was like "being trapped in a bad nightmare".

When fingerprint experts told Detective Constable Shirley McKie that her thumbprint had been found at the scene of a murder, she said it was like "being trapped in a bad nightmare".

Ms McKie knew she had never been inside the house in Kilmarnock, Scotland, where Marion Ross was murdered in 1997. She told the experts they had made a mistake.

A man was later convicted of the murder but the policewoman's steadfast refusal to accept that the doorframe print belonged to her infuriated some of her colleagues at Strathclyde Police. She was put on trial for perjury.

Ms McKie told the BBC's Crime Squad programme, which features her case tonight: "I knew it was not my fingerprint. I could not understand why they were saying it was or how this could be." A jury acquitted Ms McKie last year after an American fingerprint expert gave evidence that the print was not hers.

The detective has left Strathclyde Police on health grounds. Four fingerprint experts from the Scottish Criminal Records Office are suspended, pending an investigation into the case.

Ms McKie said: "It could happen to absolutely anyone. A normal person that does not necessarily have a police background or the help that I had would be in prison now, and that's frightening."

The case has stunned Britain's network of police fingerprint experts. Yesterday, the national head of police fingerprint training in the UK called for an overhaul of the 76-year-old system and spoke of his fears that "corners were being cut". Geoffrey Sheppard said the UK should ditch its "16-point" fingerprinting system in favour of the "non-numerical" American model.

In the UK, the 16-point system, where experts look for 16 matching marks between two prints, is widely seen as irrefutable evidence and almost always goes unchallenged in court. Under the more rigorous American system, an accredited expert gives an opinion on whether two prints match, which must be upheld by two independent experts and is open to challenge in court. The 16-point system was introduced in 1924 after a Frenchman, Alphonse Bertillion, described it in a New Zealand scientific journal, which was seen by Scotland Yard.

Mr Sheppard said: "For no scientific reason they chose the number 16. It could have been any number but we have stuck to that ever since." Some British forces use an eight-point or even six-point standard to identify prints they wish to eliminate from a crime scene.

"It's an absolute mish-mash. You either have standards or you don't," said Mr Sheppard. "The non-numerical system would rid the profession of these numbers games."

A spokesman for the Association of Chief Police Officers told The Independent it was likely to switch to the American system next year. He said: "We expect to be able to make an announcement early next year about a move to replace the numerical standard for fingerprint evidence with a system based on improved professional practice, including quality assurance and competency testing of fingerprint officers."

All fingerprint experts will also be required to go before the new London-based Council for the Registration of Forensic Practitioners, which will ensure procedures are being properly followed.

Mr Sheppard said that in a 35-year career in fingerprint, he had rarely known a defence barrister question an expert's findings. He said: "I honestly believe that the Bar Council, the Magistrates' Association, all believe the same thing: once you have got fingerprint evidence the case is closed, he's guilty."

David Wilson, a criminologist at the University of Central England, said he was surprised by the police admissions. He said: "Ultimately, fingerprint identification is a matter of opinion and what we need is a system which ensures that we get the correct opinion."