A planned new defence witness in appeals by two men jailed for murdering PSNI Constable Stephen Carroll has been "nobbled", senior judges were told today.
Lawyers for John Paul Wootton and Brendan McConville also claimed authorisation for a police surveillance operation was improperly obtained in a bid to sabotage attempts to overturn their convictions.
The allegations were made during applications for the disclosure of more material before appeal hearings get underway next month.
Constable Carroll was ambushed and shot dead as he responded to a 999 call at Lismore Manor, Craigavon in March 2009.
McConville, 42, of Glenholme Avenue in the town, is serving at least a 25 year sentence for the killing. Wootton, 22, of Collindale, Lurgan, received a minimum 14-year term.
Their joint appeal was originally due to be heard in April.
But days before it a man related to a key prosecution witness was arrested and held for two days before being released without charge.
This man, who cannot be identified, has made a sworn court statement branding his relative a compulsive liar.
According to defence lawyers police arrested him in a bid to pressure him into withdrawing his evidence, and warned he would be discredited if he testified.
In the Court of Appeal today Barry Macdonald QC told judges why he does not want to come to court.
"The use the vernacular, this witness has been nobbled by the prosecution or the police," he said.
Counsel for the prosecution argued, however, that he could have been called at the original trial.
He confirmed that the reliability of the statement now given by this man is being questioned.
The barrister said it was being alleged: "Either that he was coerced in some way or was co-operating willingly in effectively attempting to pervert the course of justice."
He acknowledged the prosecution was not alleging any coercion occurred at a series of meetings with defence solictors.
Instead, he claimed it was "inferential" from the available evidence.
During the hearing Mr Macdonald identified issues over the amount of audio and video recordings disclosed from a covert police operation on the new witness.
Particular questions were raised over why no material was available from the day in April when officers called at a home to speak to him.
"The relevance is to show the demeanour of (the man). He was not a man under pressure," Mr Macdonald explained.
Prosecution counsel insisted there was no further material available.
Lord Chief Justice Sir Declan Morgan, sitting with Lord Justices Higgins and Coghlin, suggested it may be surprising that no recordings were carried out on the day police went to the house.
The barrister replied: "For the rather prosaic reason... in the sense there was no other audio sought that day."
Dealing with the defence applications, Sir Declan said the issues surrounding surveillance authorisation under the Regulation of Investigatory Powers Act (RIPA) would be kept under review.
He added: "We are not prepared at this stage to order disclosure in relation to the remaining matters sought in light of prosecution indications given to us."