By Tom Gordon, Scottish Political Editor

KEY papers from the unjust prosecution of policewoman Shirley McKie have gone missing from the Crown Office, it has emerged.

Parts of the indicting file, which recorded the detailed thinking of prosecutors before McKie's trial for perjury, disappeared at least four years ago, but the absence has only now been admitted.

The revelation came in testimony before the fingerprint inquiry, the official investigation into the McKie scandal.

McKie, a former detective constable, was tried and acquitted for perjury in 1999 after denying she left a thumb print at the home of murdered Kilmarnock woman Marion Ross in 1997.

Her refusal to accept that the print was hers cast doubt on fingerprint identification by the Scottish Criminal Records Office (SCRO). Her acquittal undermined the conviction of David Asbury for Ross's murder. McKie's defence team successfully challenged the SCRO opinion using other expert witnesses.

McKie received £750,000 compensation for the loss of her career in 2006, and Asbury's conviction was also quashed.

Now Gillian Climie, a procurator-fiscal depute who prepared the prosecution case against McKie, has revealed the file of her working notes and drafts has disappeared.

In a witness statement read to the inquiry, she said: "I understand that the Crown Office High Court Unit indicting file' for Ms McKie is missing (and has been missing since 2005 or earlier, this information was supplied to me by Crown Office when I inquired in March 2009)."

In later oral evidence, Climie was questioned by Ailsa Carmichael, the junior counsel to the inquiry, who said: "We don't have the file that covers the period when Ms McKie was actually indicted."

Climie replied: "And I'm very disappointed about that as well because it puts me in a very difficult position."

Sir Anthony Campbell, the inquiry chair, then intervened: "We are very conscious of that. It is regrettable that we don't have it."

Climie also said she felt it was not in the public interest to prosecute McKie, as a police disciplinary hearing would have been better.

"The McKie case has been a tragedy for the Scottish criminal justice system as a whole and a personal tragedy for Ms McKie and for the SCRO experts directly involved," she said.

The missing paperwork covers the six months leading up to McKie's prosecution in April 1999.

A Crown Office spokesman said: "It is not the case that the whole High Court file for the McKie case is missing; the outer cover for the McKie High Court file is no longer available.

"Unfortunately, it appears that some papers relating to the prosecution of Shirley McKie originally contained within the folder are missing.

"The consideration of available written and oral evidence is a matter for the inquiry and it would be inappropriate for us to comment further at this stage."