A written account of an interview with Silcott, supposed to be a contemporaneous note, was later altered to include damaging comments which he had not made and was used as evidence against him at the Old Bailey in 1987.
Yesterday the two officers principally responsible for Silcott's conviction, which was quashed by the Court of Appeal in 1991, were themselves in the dock.
Detective Chief Superintendent Graham Melvin, 52, and Detective Inspector Maxwell Dingle, 57, are pleading not guilty to conspiracy to pervert the course of public justice. Det Chief Supt Melvin also denies perjury.
David Calvert-Smith, for the prosecution, told the court that in October 1985 there had been a riot on the Broadwater Farm Estate in north London, during which PC Blakelock had been brutally murdered.
Det Chief Supt Melvin and Det Insp Dingle were called in to investigate the murder. Six days after the riot Silcott was arrested and was interviewed five times during the next 24 hours, Det Chief Supt Melvin asking the questions and Det Insp Dingle making the notes.
During the first four interviews Silcott refused to answer most questions or sign the notes. But the police account of the fifth interview was very different.
According to the note, Det Chief Supt Melvin said to Silcott that he was one of those standing over PC Blakelock and struck him with either a machete or a sword- type weapon. Silcott allegedly replied: 'Who told you that?'
When told that police had information that he had been actively involved in the murder Silcott was said to have answered: 'They are only kids. No one is going to believe them.'
He was said to have paced around, sworn, cried and said 'Jesus, Jesus' before telling the detectives:'You ain't got enough evidence. Those kids will never go to court, you wait and see.'
Mr Calvert-Smith said: 'There appears on the face of it to have been a distinct change in the attitude of Mr Silcott.
'The Crown's contention is that these pages were fabricated. They were not what Mr Silcott had to say at all, they were written after the event in order to make a stronger case against him.'
Both defendants made statements declaring that the notes of the interviews were true and Det Chief Supt Melvin gave evidence at Silcott's trial that they had been made at the time.
Four years later the notes were examined by experts using a technique called ESDA (Electrostatic Deposition/Detection Analysis) which detects a small electrostatic charge left on a page when someone writes on the sheet above it.
On pages three to six of the note of the fifth interview there were no impressions from earlier pages which there were throughout the rest of the series. The forms on which they were written were a different type of paper from the rest of the report.
The analysis also revealed an imprint of a different page five from the one submitted in evidence which was clearly the same interview with Silcott but in which he made no implicit admissions.
Laser tests showed the imprint of another officer's endorsement on the back of one of the allegedly false pages. The officer had to sign the notes because Silcott would not do so, but the imprint showed that the page had been written after he had approved the document.
The case continues today.
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