In a decision that is likely to prompt appeals to the House of Lords and European Court of Human Rights, the Lord Chief Justice, Lord Taylor, said that in some 'exceptional' cases information could be withheld from the defence. This was a reversal of a ruling made by the Court of Appeal last year in the Judith Ward case.
Ms Ward was released in May 1992 after being wrongly convicted of the M62 coach bombing. Evidence pointing to her innocence was withheld from the defence for 18 years.
Lord Taylor, sitting in the Court of Appeal with Mr Justice Owen and Mr Justice Curtis, said: 'In our view the judgment in Ward went too far in accepting . . . the general rule requiring notice to the defence admitted of no qualification or exception.'
Lord Taylor gave his judgment after ruling that new evidence relating to the conviction of three men for the 'M25 gang' crimes should not be disclosed to the defence.
Raphael Rowe, 24, Michael Davis, 26, and Randolph Johnson, 27, all from Sydenham, south-east London, were sentenced to life imprisonment in March 1990 for murder, robbery, grievous bodily harm and firearm offences after a series of attacks close to the M25 motorway on the night of 15 December 1988. Their appeal will be heard on 25 January.
Michael Mansfield QC, for Rowe and Davis, said that the prosecution should always tell defence lawyers the nature of the evidence even it was not disclosed in detail. 'The Crown must at the very least reveal the category of the material so the defence can make some sort of representation on why it should be disclosed and why it is relevant to the case.
'If that does not happen we are in an impossible situation,' Mr Mansfield added.
Although Lord Taylor accepted that, in the majority of cases, this requirement should be met, he ruled that in 'exceptionally sensitive cases', the prosecution did not have to tell the defence anything about the evidence. This was the situation in the M25 case, he said.
Lord Taylor added that in some 'rare' cases the prosecution did not even have to inform the defence that the evidence existed because it could 'let the cat out of the bag'. This might apply when the information may damage the interests of the country.
In such cases, the prosecution will discuss the evidence with a judge, who will then decide whether the defence should be told of its existence. The court should continually monitor the situation in case the hearing changed direction and the evidence may need to be disclosed.
'Issues may emerge so that the public interest in non-disclosure may be eclipsed by the need to disclose in the interests of securing fairness to the defendant,' Lord Taylor said.
He said that he recognised open justice required maximum disclosure wherever possible. 'However, in regard to public interest immunity in criminal cases, it is implicit that the defence cannot have the fullest information without pre-empting the outcome of the application.'
Liberty, formerly the National Council for Civil Liberties, believes that the three men convicted in the M25 case are innocent, and said that the judgment would lead to further miscarriages of justice.
John Wadham, Liberty's legal officer, said: 'The defence will not be able to rely upon the judge and the prosecution to protect the defendant's rights in these secret meetings.'