Police killer Harry Roberts has lost his appeal to the House of Lords over the use of secret evidence to keep him in jail.
Roberts has served 39 years for the three murders
Roberts, 69, is serving life for the murder of three policemen in Shepherd's Bush, west London, in 1966, but his 30-year tariff expired nine years ago.
His lawyers challenged the appointment of a special advocate who viewed secret evidence on Roberts' behalf.
But on Thursday Law Lords ruled against him by a majority of three to two.
The Parole Board had said sources would be at risk if the secret evidence was handed over.
Lord Bingham, Lord Woolf, Lord Steyn, Lord Rodger and Lord Carswell ruled on Roberts' appeal.
There was speculation the case, which was heard at the House of Lords in April, could have implications for the use of special advocates in the future.
They have been used in deportation cases where secret intelligence has been used, and also in the controversial decisions whether to keep foreign nationals detained under anti-terrorist legislation.
They are able to see secret material but are not able to discuss it with defendants or their legal advisers.
Roberts' victims - Det Con David Wombwell, Sgt Christopher Head and Pc Geoffrey Fox
Human rights analysts have complained that detaining someone without telling them the nature of the charge or the evidence against them is against the nature of the UK's justice system.
But last July, the Court of Appeal ruled the use of a special advocate in Roberts' case was not unfair, even though the case did not involve national security.
It said the safety of the sources of the secret material was at risk if Roberts or his representatives were able to see the evidence.
In 2001 Roberts had been transferred to an open prison in what was thought to be a prelude to his release.
But he was alleged to have been involved in drug dealing, bringing contraband into prison and other activities which jeopardised his release.
He was sent back to a closed prison pending a review from then Home Secretary David Blunkett, who produced the material withheld from Roberts.
The Parole Board ruled the material could only be seen by a special advocate.
Roberts was jailed for murdering Pc Geoffrey Fox, 41, Sgt Christopher Head, 30, and Det Con David Wombwell, 25.
The murder of the three plain-clothes officers was one of the most high-profile crimes of the 1960s.
The officers were gunned down in front of children playing in a street, after they had pulled over a van containing Roberts and two other men following an armed robbery.