Gardai have now arrested a total of 16 people for withholding information about the savage knife murder of Lorcan O'Reilly.
The respectable 21-year-old was stabbed to death on Halloween but officers have faced a wall of silence as they continue their investigations.
Those arrested for withholding information include women and juveniles.
"Gardai will keep plugging away on this investigation. It would be a lot more simpler if there was co-operation from key witnesses but this is not happening," a source explained. "People will continue to be arrested if it is suspected that they witnessed this crime or have information about it."
Lorcan was stabbed to death when he tried to break up a fight in Dublin's Oliver Bond Street flats complex at 2.45am on November 1.
The chief suspect for the brutal murder is a 16-year-old youth who has close links to gangster 'Fat' Freddie Thompson.
The Herald previously revealed that this teenager presented himself to Kevin Street Garda Station for questioning with his two grandmothers.
However, officers declined to take a statement from the teenager. They intend to collect more evidence before questioning him about the murder.
Since then, it is understood that potential witnesses have been subject to widespread intimidation.
It is believed that 'Fat' Freddie Thompson was back in the capital for Christmas but has been "keeping his head down", a source said.
Lorcan O'Reilly, who was from Robert Emmet Close in the south inner city, was a highly respected young man. A huge crowd of mourners attended his funeral mass where Fr Richie Good spoke about the shocking case.
"There is something essentially wrong about what happened to Lorcan," said Fr Goode. "There should be no reason for us to be here.
"All we can do is cry, and ask the question why did this happen. The reason it happened was Lorcan was true to his nature. Lorcan was a peacemaker," he added.
"It was acting as peacemaker that brought on this tragedy that cost him his life."
Gifts brought to the altar to celebrate Lorcan's life were a model motorbike, a jacket and a set of earphones in the highly-emotional ceremony in a packed city church.