The foreman of the jury brought it to the attention of the trial judge, Judge Seán Ó Donnabháin, that the female juror had seen certain matters on the internet.
The judge is now considering the question of holding her in contempt of court for her behaviour.
The jury had been warned not to look up any aspect of the case on the internet.
Judge Ó Donnabháin granted the juror free legal aid to get a lawyer to represent her in court today.
“As you know your behaviour has caused the jury to be discharged. I think you should have a solicitor. I will give you free legal aid to get a solicitor.
“Tell your solicitor that because you spoke to the jury as a result of access to Facebook despite a warning the judge gave you, the judge is taking a serious view of this and has to take a view on whether or not you are in contempt of court,” said Judge Ó Donnabháin.
The jury had been deliberating on Wednesday afternoon and were told to return to Cork Circuit Criminal Court yesterday morning to resume their deliberations.
For legal reasons at this stage it is not possible to report on details of the collapsed trial.
In such circumstances, trials are often listed for retrial a few months later.