A court case involving a convicted IRA member has collapsed after a juror received a threatening phone call warning he would be harmed if the man was found guilty.

The Sunday Tribune has learned a jury in the Circuit Criminal Court was discharged last Monday after the juror went to the gardaí and informed them threats had been made to him.

The court case had been going on for three days and the jury was being directed by the trial judge on Friday 28 November when he adjourned the case for the weekend.

Last Sunday evening the juror received a phone call from a man who was known to him and was told there would be serious consequences if the defendant was found guilty.

The juror immediately contacted the gardaí and an investigation involving three Dublin garda stations was launched.

The man who is alleged to have made the phone call was arrested and questioned before being released without charge pending a decision from the director of public prosecutions about any charges.

He is not the man who was on trial.

Last Monday morning the trial judge was informed of the weekend's developments and he immediately discharged the jury. The case has been put back for mention until January of next year.

Gardaí are believed to be considering making an application to try the case in the non-jury Special Criminal Court because of the alleged jury intimidation.

The man in question was before the court on serious charges.

He is a convicted IRA member with previous convictions for possession of firearms. He was controversially released early under the Good Friday agreement in 1995 after serving just over half of his sentence.

Although there are several dozen cases each year of witness intimidation, incidents of plots to tamper and interfere with jurors are extremely rare.

In June 2006, two men attending the trial of Bernard Dempsey for the murder of a man in a Dublin pub were arrested and detained for the duration of the trial after being overheard by a garda talking about "getting the jury f**ked up".

In July 2005, 45-year-old James Walsh from Rathfarnham was jailed for four years for attempting to influence a juror in a criminal trial. Judge Thomas McDonagh said the attempt to influence the juror was to "attack one of the fundamental pillars of the Irish justice system".

He said the incident was "as serious an attack as can be imagined" on the justice system and said the sentence had to reflect that fact.