The jury in the trial of barrister and part-time judge, Constance Briscoe, has been discharged after failing to decide if she perverted the course of justice.
Ms Briscoe, 56, is accused of lying to police investigating the former cabinet minister Chris Huhne, who got his wife to take speeding points for him.
She denies three counts of intending to pervert the course of justice.
Prosecutor Bobbie Cheema QC said there would have to be a retrial.
The jury of six women and five men had been deliberating since Wednesday at Southwark Crown Court, but failed to reach verdicts on any of the counts.
Ms Briscoe has been suspended from the Bar since her arrest in October 2012.
In February last year, Mr Huhne pleaded guilty to perverting the course of justice after he swapped his speeding points with Ms Pryce.
Ms Pryce, who had denied the same charge, was convicted in March.
Both were jailed and have since been released.
During Ms Briscoe's trial, the court has heard she helped Ms Pryce, a friend and neighbour in Clapham, London, to reveal information about Mr Huhne's points-swapping to newspapers after the couple separated in 2010.
She is accused of providing police with two inaccurate statements about the role she played as an intermediary between Ms Pryce and reporters.
The prosecution also allege she produced a doctored copy of a statement, and then deliberately had a document expert view the wrong version of the statement.
During their 13-hour deliberation the jury asked the judge five questions about either the law or evidence they had heard.
BBC legal correspondent Clive Coleman said a new trial date of 1 May 2014 had been proposed.