The European Parliament president has praised the bravery of the family of Robert McCartney from Belfast after meeting his sisters in Brussels.
The McCartney sisters met the European Parliament president
Josep Borrell said the family had the full support of the European Parliament in their campaign.
The McCartneys blame IRA members for the murder and subsequent interference with evidence and witnesses.
Catherine, Gemma and Paula McCartney received a standing ovation after addressing a group of MEPs.
The sisters met Mr Borrell for about 20 minutes on Wednesday.
Afterwards, he said: "I am deeply impressed by the bravery they show in standing up to impunity and by the campaign for justice they are leading.
"Violence must be fought and condemned in all countries, by all means.
"The doors of the European Parliament will always be open to those who need a public tribune to fight any kind of injustice."
Robert McCartney, 33, was killed near Belfast city centre
Mr McCartney, 33, was stabbed to death in Belfast city centre on 30 January.
The McCartneys are trying to raise financial support to begin a civil action against those they believe were responsible for the murder.
Mr Borrell is to take part in talks on Thursday to assess whether there are ways to use the European Parliament budget to help individual cases.
Earlier, Catherine McCartney told the European Socialist Group peace deals "meant nothing" if ordinary people could be murdered and justice not be done.
She called for Sinn Fein to take more action against members who were in the bar and who had not helped police.
The meeting was also addressed by Proinsias De Rossa of the Irish Labour Party, who urged the group to consider financial help for the campaign and putting forward the type of resolution that Senator Ted Kennedy put forward in America.
Mr Kennedy proposed a resolution, passed by the US Senate, condeming IRA violence and called on Sinn Fein to help police catch Mr McCartney's killers.
The sisters met leading European politicians in their campaign for justice as well as European Commission president Jose Manuel Barroso.
They also met the much smaller Nordic Green Group of which Sinn Fein MEPs Bairbre de Brun and Mary Lou McDonald are members.
The group offered its "solidarity" to the sisters but they told Ms de Brun and other assembled MEPs that Sinn Fein as a democratic political party should use their power to make witnesses from the bar co-operate with the police.
Ms de Brun denied the presence of the McCartneys in Europe was an embarassment to her party and said that she was committed to winning justice for them.
So far, police investigating the murder have arrested and questioned 12 men, all of whom were released without charge.
The IRA has expelled three members over the stabbing and Sinn Fein subsequently suspended seven of its members.