"It's not over," vowed Catherine McCartney when republican Terence Davison walked free after being cleared of murdering her brother.

The 33-year-old father-of-two was stabbed to death in a Belfast street after a row in Magennis's Bar close to the republican Markets area on January 30 2005.

The sisters - who took their campaign for justice for their brother across the globe and into the White House - believe at least 15 people were involved in the murder and a near forensic clean-up of the scene to remove evidence, and remain at large.

They challenged the IRA and Sinn Fein to stop blocking investigations and to co-operate with the police. Ms McCartney vowed not to let things rest despite it having "become an embarrassment to the British and Irish Governments".

Speaking on behalf of her sisters after the acquittal at Belfast Crown Court, Ms McCartney said they were very disappointed but not surprised.

"We hadn't got very high expectations," she said. "As a lay person sitting in that court listening to the evidence we have heard, would I have put someone away on that evidence? No. I wouldn't have so I can't expect the judge to do so."

The blame lay firmly with the IRA and Sinn Fein who, she said, "from day one have obstructed the course of justice and continue to do so".

"We believe there is still a body of evidence out there that can still be brought forward and we expect Sinn Fein to do what they say they can do, despite their having refused to do so up to date," she said. "Despite saying to the police they would co-operate they have not co-operated whatsoever."

In a judgment taking more than two hours to deliver, Mr Justice John Gillen acquitted Davison of murder and two further counts of affray. Co-accused James McCormick, 39, and Joseph Fitzpatrick, 47, were also found not guilty of affray. Fitzpatrick was acquitted on a further charge of assault.