The sister of a man murdered outside a Belfast pub two weeks ago has accused republicans of working to shield his killers from the PSNI investigation.
Leading a chorus of calls for the guilty to face justice, Ms Paula McCartney said the killers of her brother, Robert, were "believing they are going to get away with this".
Mr McCartney (33) was stabbed following a dispute in a bar. He died the following day and the PSNI began a murder inquiry.
Ms McCartney endorsed a police view of her brother's murder: "If it wasn't related to any organisation people would now be arrested and charged. I don't believe that the IRA sanctioned this, but they have to accept that members of it carried this out."
She insisted republicans had worked to frustrate the murder inquiry. "Their cover-up and their clean-up operation afterwards was meticulous," she said.
"It's just getting more evidence and getting more people to come forward and be brave and hand these people over.
"They're no good to man nor beast - they're just psychopaths with power," she told BBC Radio Ulster.
Seven people have been arrested in connection with the murder, including a senior republican, but there have been no charges. The murder weapon has not been found and the police have refused to comment on claims that video evidence from a camera at Magennis's Bar in the city centre, where the murder took place, has gone missing.
It has also been claimed that of the dozens of people in the bar on Sunday, January 30th, when the murder took place, none has come forward.
Ms McCartney accused Sinn Féin of putting pressure on witnesses not to come forward.
Sinn Féin's Mr Gerry Kelly, a North Belfast Assembly member, denied his party wanted to frustrate the murder investigation. He said it did not matter if republicans or loyalists were responsible for the murder. "It is absolutely wrong and the community should reject it," he said.
Politicians on all sides have accused republicans of orchestrating street violence as police tried to search houses in the Markets and Short Strand areas. Sinn Féin, meanwhile, has accused the police of heavy-handedness.
The SDLP leader, Mr Mark Durkan, has vowed to help the family secure justice. "Not the so-called justice of the Provisionals but justice under the law.
After meeting the family he said: "His vicious murder was at the hands of IRA people, including a very senior IRA person who was centrally involved in the attack. Many of those IRA people have been prominent Sinn Féin election workers and minders for their politicians.
He added: "The family are equally clear as to why Robert was killed. Simply because he refused to bend the knee to a Provo boss. This is the worst kind of oppression by the IRA of their own community.
"It is a frightening example of the Mafia culture that is tearing away at our communities and threatening decent people. We share their outrage that the Provisional movement is again not simply trying to evade the law, but actually hold their members above it."
Mr Durkan said he would brief the US special envoy Dr Mitchell Reiss next week during a visit to Washington.