The Assembly has passed an SDLP motion condemning the murder of south Armagh man Paul Quinn and stating he was not a criminal.
Sinn Féin did not support the other parties and Independents who backed the motion. The debate was watched from the public gallery by Mr Quinn's parents and their support group.
Despite restated claims from Sinn Féin that there was no IRA link to the killing, DUP speakers warned the issue could yet provide a serious problem for the Executive. East Derry MP Gregory Campbell said proven IRA involvement in the murder "could precipitate a crisis".
Newry and Armagh Assembly member Dominic Bradley told the House there was no one in south Armagh who did not believe that the IRA was not involved in the murder. He said Newry and Armagh MP Conor Murphy (SF) was naive in accepting IRA assurances it was not involved.
Mr Murphy should set the record straight in relation to the murder victim, Mr Bradley said. Lagan Valley MP Jeffrey Donaldson said: "The DUP will not ignore the murder of Paul Quinn." Mr Murphy told the Assembly he "completely condemned the murder" and called on the killers to co-operate with the police.However, the calling of the debate was "divisive and selective". "This politicking does not serve the search for truth well," he said. "I call for people to assist the gardaí and PSNI."
Alliance leader David Ford claimed Sinn Féin "could not find it in their hearts to apologise for their slur against Paul Quinn".
Former Sinn Féin Assembly member Gerry McHugh called on Sinn Féin president Gerry Adams to "retract the criminal label".
Stephen Quinn, father of the murdered man, said Mr Murphy's decision to leave the chamber after his speech was "disgraceful".