The trial of a 24-year-old woman for careless driving causing the death of her younger friend over three years ago on the Cork-Kerry border has collapsed after the jury received a prosecution exhibit document, part of which they should not have seen.

This afternoon, trial judge Thomas E O'Donnell recalled the jury of five men and seven women. They had been sworn in on Tuesday.

The judge apologised to them but said he had no choice but to discharge them after an application by the defence.

The trial of mother-of-one Sarah O'Connell was on its third day.

The prosecution had closed its case and closing speeches from the prosecution and defence were heard yesterday.

Judge Thomas O' Donnell charged the jury this morning, summing up the evidence and speaking about the distinction between dangerous driving and the lesser charge of driving without due care, and which the jury had to deliberate on.

The 12 were handed the exhibits in the case including statements and a memo of a garda interview with the accused. They were sent out to begin their deliberations at 11.40am.

After just over an hour of deliberation, the jury returned asking for clarification on whether a momentary lapse of concentration could amount to careless driving.

Judge O'Donnell advised them on this and on the case law pertaining to it and told them they were the arbiters of the facts. The jury were sent to lunch under guard.  

After lunch, but before restarting deliberations, the foreman of the jury asked the judge about a prosecution exhibit, a memo of an interview, which he said the jury had received and parts of which had been scribbled out.

The 12 jurors were sent to their room and, after consultation between the legal teams, Senior Counsel Mark Nichols for the defence told Judge O'Donnell he was applying for a discharge of the jury.

There was a brief discussion in front of the judge, but ex jury, about the defence application.

At 2.40pm, the jury were recalled and Judge O'Donnell said he wished to speak to them "in respect of the matter regarding the memo of interview and the parts scribbled out".

"From time to time, there's agreement between the defence and the prosecution on matters," the judge said.

It had been agreed that a section of the memo should go out and the jurors had been given the edited document.

Unfortunately, they had also been given an item they should not have, the judge said, referring to the scribbled on, or unedited, document which had been included also in the exhibits.

"The defence has made an application to discharge the jury," the judge said.

"This has happened and I am sorry about that but there's nothing I can do about it," Judge O'Donnell told them.

He thanked them and excused them from jury service for a period of five years, before formally discharging them.

Accused woman Sarah O'Connell was told she could stand down and she left the dock to join her grandfather and mother.

Sarah O'Connell of Sean Moylan Park, Mallow, Co. Cork, had pleaded not guilty to the charge of careless driving causing the death of 14-year-old Caitlin Taylor, of Gouldshill, Mallow at Knockeenahone, Scartaglen on 15 June 2014.

The matter has been put back to the call-over list of 15 January next at the Circuit Criminal Court in Tralee to fix a date for a new trial, and Ms O'Connell has been remanded on continuing bail.