Sinn Fein has been slammed for describing the prosecution of a killer who shot a police officer after visiting his newborn son as "vindictive".
Seamus Martin Kearney (57), of Gorteade Road, Maghera, was found guilty at Belfast Crown Court of the IRA murder of RUC reserve constable John Proctor as he left a hospital in 1981.
Kearney was also found guilty of the possession of an Armalite AR15 rifle and ammunition with intent to endanger life.
He remained expressionless, staring straight ahead in the dock while Judge David McFarland told him being found guilty of murder carried a mandatory life sentence.
The tariff will be confirmed next month. However, under the terms of the Good Friday Agreement it is likely that Kearney will serve just two years.
In his 23-page ruling, Judge McFarland said there were three strands of evidence against Kearney: DNA from a cigarette butt found at the scene, the defendant's bad character, and the inferences to be drawn from his failure to give evidence.
A re-investigation of the murder by the Historical Enquiries Team was able to use modern forensic techniques to extract a DNA profile from a cigarette butt thrown away at the scene.
DUP victims' spokesman Jeffrey Donaldson reacted with disgust yesterday when Sinn Fein criticised the conviction and called for Kearney to be released.
Kearney was previously jailed in December 1984 for the attempted murder of UDR soldiers, whose Land Rover came under fire from the same AR15 rifle used to kill Constable Proctor, in November 1982. Sinn Fein South Derry MLA Ian Milne strongly criticised the conviction of Kearney.
"I know Seamus Kearney well. He previously served a long period of imprisonment for IRA activities. The decision to pursue Seamus on these historic charges was wrong, vindictive, unnecessary and counterproductive."
Mr Milne, who was convicted of the murder of a UDR soldier in 1977, claimed that the Government is "continuing to fight old battles".
"It is ironic at a time when the Haass process is coming to a conclusion in dealing with legacy issues that a republican is being imprisoned on historic charges," he said.
"It seems that the British Government wants to talk the language of building a new future here, but at the same time is sending a message that it is continuing to fight old battles.
"Like the previous case of Gerry McGeough, it is our position that Seamus should be released and allowed to return home to his family." Mr Donaldson hit back at the comments, accusing Sinn Fein of showing a "callous disregard for the suffering and pain inflicted by the IRA on Mr Proctor's family".
"It is disgraceful to see elected representatives rushing out Press releases demanding the release of this convicted murderer," he said.
"The fact that a Sinn Fein MLA couldn't even mention Mr Proctor by name in his Press release speaks volumes: he was just another RUC man to their mind."
Mr Donaldson insisted that Sinn Fein would not be allowed to "rewrite history". "We have seen this pattern of behaviour before when republicans are held to account for their past: the treatment of councillor Sammy Brush, who had to endure a motion being passed in the council he serves on calling for the release of the man who tried to murder him was outrageous.
"Similarly, the contempt heaped upon Ann Travers at the time of the Special Advisers Bill by online Sinn Fein supporters was obscene."
In finding Kearney guilty, Judge McFarland said he was satisfied "beyond reasonable doubt that the defendant had smoked the cigarette, and having finished smoking it discarded it at or about the time of the shooting".
"In all likelihood it was smoked when the defendant was waiting for John Proctor to leave the hospital," he said.
"I am firmly convinced the defendant was either the gunman, the driver of the Ford Escort or was an occupant of the car being present to provide support for the planned killing.
"In any event, he is guilty of the murder of John Proctor."
Constable Proctor's family wept with joy at the guilty verdict.