Sinn Fein leader Gerry Adams today said anyone with information about Robert McCartney's murder should go to the police investigating it.
With Sinn Fein facing demands to prove its new backing for policing was genuine, the party president clearly urged full support for detectives hunting the IRA gang blamed for stabbing the father-of-two outside a central Belfast pub.
The murder in January 2005 plunged the republican movement into crisis amid allegations that the killers were shielded.
Even though up to 70 people were in Magennis's Bar on the night Mr McCartney (33) was attacked, witnesses have so far refused to speak to police.
But after the murdered man's sister Catherine described republican assistance with the probe as the acid test of Sinn Fein's new decision to end generations of opposition to the force, Mr Adams responded to the challenge.
He said: "Anybody who has any information about the McCartney killing should give it to the police." His call marked a major advance from the party's position at the time of the murder, when it refused to recommend contacting the police service.
It could also heighten pressure on Ian Paisley's Democratic Unionists to acknowledge Sinn Fein is fit to share power with them in a new Stormont administration.
Full co-operation by republicans with the McCartney murder inquiry has been seen as one of the tests set by the DUP as it assesses the impact of Sinn Fein's overwhelming endorsement of policing before deciding to enter a coalition government.
Earlier, the Minister for Justice Michael McDowell echoed Catherine McCartney's challenge to the republican movement over the murder.
But Mr Adams hit back by insisting Mr McDowell should not be setting tests for anyone. "This is the minister who refuses to put into place in the other jurisdiction on this island the type of accountability and mechanisms that are in place in this one.