A juror who allegedly contacted a defendant via Facebook faces Contempt of Court proceedings in a legal first.
Joanne Fraill is accused of contacting Jamie Sewart, a defendant in a trial that subsequently collapsed.
The contact led the judge to discharge the jury in the massive 10-week drugs trial.
The pair face up to two years in prison if found guilty at the hearing at the High Court in London on Tuesday.
The case, brought by the Attorney General Dominic Grieve QC, is being heard by the Lord Chief Justice, Lord Judge.
Another man who was convicted and jailed in the case is appealing, claiming jury misconduct in the aborted trial that took place last year in Manchester.
Earlier this year, the attorney general sought permission at the High Court to bring the proceedings against Ms Frail, of Blackley, Manchester, and Ms Sewart, of Bolton.
The alleged contact occurred after Ms Sewart had already been acquitted but the jury had still to reach verdicts on other defendants.
Ms Fraill is also said to have conducted internet research on defendants, despite instructions from the judge to only decide the case on the evidence in court.
Angus McCullough QC, for the attorney general, told the High Court: "Ms Fraill contacted Ms Sewart via the internet and conducted an online conversation with her.
"The discussion took place at a time when the jury still had outstanding verdicts to return on the case.
"That contact and discussion were in direct breach of the judge's repeated directions to the jury that they should not discuss the case with anyone outside their number, and constituted a contempt of court.
"Ms Fraill also conducted internet searches on the defendants she was trying."
In a speech last year, the Lord Chief Justice warned that jurors could go to jail if they searched the internet for information on defendants. At the time of the speech, he said that he knew of one rape trial which had been stopped because of online research by jurors.
"It is at least arguable that for a juror to examine the internet for information relating to the case is a contempt of court, and a criminal contempt," he said.
"One consequence of the use, or rather misuse of modern technology in the course of the trial would be that they may be liable to a finding of contempt of court, and indeed a sentence."
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