They include the claims of a local housing officer who went to the dead man's house on Tuesday November 7. She and a colleague looked through Forsyth's window, directly at the site where his body was supposed to be, but saw no corpse.

Another witness, a local shopkeeper, told police he last saw Forsyth alive on Saturday, November 4. The police told the shopkeeper that this was "impossible". Johnston's lawyer, Stephen Morrison, said: "They tried to convince him that he couldn't have been right but he feels he is 99% right."

A third witness claims in her statement that she saw Forsyth as she was making her way to work on Thursday November 9. A fourth statement also implies that yet another witness saw Forsyth alive on November 4.

There was no forensic evidence linking Johnston to the killing. The blood of two different people was found in the victim's house - neither type matched Forsyth or Johnston, who had no history of violent crime.

An independent post mortem showed that Forsyth probably died sometime after Tuesday November 7 and certainly not before Sunday November 5. The Sunday Herald has also discovered that Fife Constabulary attempted to suppress other evidence from a further six witnesses prior to the murder trial. After a chance conversation, says Morrison, the defence did manage to locate these witnesses and they appeared in court.

In a letter dated February 3 1997 from the Crown Office, Deputy Crown Agent Norman McFadyen says he met with the Deputy Chief Constable of Fife Constabulary, Graham Bennet, adding with reference to the initial six witnesses: "The Lord Advocate and I are in no doubt that the information which was provided to the police by the witnesses in this case should indeed have been drawn to the attention of the procurator fiscal".

McFadyen goes on to admit that the Crown was not aware that the police had suppressed material, adding: "The Lord Advocate has instructed that it be made clear to the Chief Constable that it is wholly unacceptable that misleading information was given to the procurator fiscal when these matters were raised."

Morrison said: "This seems a clear cut case of deliberate suppression of evidence. If that is the case then it is a criminal offence and a conspiracy to pervert the course of justice. My client is very bitter and angry, but he believes he will soon be out of prison and his name cleared."

Lord Fraser of Carmyle, the former Lord Advocate, said: "The alleged conduct by Fife Constabulary is totally fatal to the interests of justice and utterly wrong in practice.

"It is not difficult to conceive of circumstances where withholding information might be seen as an attempt to pervert the course of justice. There is a disturbing practice in Scottish police where they fail to understand that all information must be conveyed to the Crown.

"It is not the job of the police to decide what to send to the Lord Advocate and what to keep from him. The police must get this into their heads. We need an immediate investigation into this case to find out if this was a case of incompetence or something more sinister. If this was deliberate there should be a criminal inquiry. From now on it must be a disciplinary, if not criminal offence, for the police to fail to pass on evidence. By behaving like this the police are usurping the role of the judge, the jury and justice itself."

The SNP's justice spokesman, Michael Matheson, said: "The officers involved must be immediately suspended pending the outcome of an inquiry. This goes right to the heart of the administration of an open and fair justice system. It is the most cynical approach to justice I have ever heard of - it is reminiscent of what went on in the Gulag system of the former Soviet Union."

Phil Gallie, Tory justice spokesman, said: "We need an investigation into the way the police weeded out these statements. There are obvious grounds for appeal now. If the appeal is upheld then we need to look at a criminal investigation."

John Scott, chair of the Scottish Human Rights Centre, said: "Steven Johnston's case should be referred to Court of Appeal as soon as possible." more..