The murder of south Armagh man Paul Quinn is a test for republicans and the peace process, according to the opposition leader in the Republic.
Paul Quinn was beaten to death in October
Mr Quinn, 21, from Cullyhanna, died after being attacked and beaten at a shed near Castleblayney in October.
His family have blamed members of the IRA - but Sinn Fein deny this.
Fine Gael leader Enda Kenny told the Dail that the murder was "pre-meditated savagery" and questioned some republicans' commitment to peace.
"It is a real litmus test for the peace process," he said.
"You cannot have a situation where a peace process exists and where people are afraid to whisper, are afraid to speak out on the basis that it might unravel.
"A peace process is not a peace process if it delivers bad justice."
Justice Minister Brian Lenihan urged people with information on the murder to come forward.
"It is vitally important that people with
information which might help find the people responsible and bring them to
justice make it known," he said.
"I include those who may not have been directly involved but nonetheless are
party to what could be vital information."
Gardai, who are co-operating closely with the PSNI, are pursuing 1,200 lines of
inquiry into the murder and have taken more than 400 statements.
Sinn Fein TD Caoimhghin O'Caolain condemned the murder and called for witnesses
to come forward.
"It shocked and sickened people in the border counties and throughout Ireland.
"It was a despicable act of brutality and murder carried out by people who
deserve only the contempt and the condemnation of society."