One of the country's top female judges tried to dupe jurors by deliberately giving an expert the wrong copy of a statement to ensure his report would back up her claims, a court has heard.
Constance Briscoe, 56, from Clapham, gave the handwriting expert a copy of a witness statement under "false pretences" so his findings would be in her favour, it is alleged.
The charges relate to her role in exposing how ex-cabinet minister Chris Huhne swapped speeding points.
She denies three counts of intending to pervert the course of justice.
Prosecutors at Southwark Crown Court said Ms Briscoe helped her friend and neighbour Vicky Pryce reveal information to the press.
Bobbie Cheema, prosecuting, told the jury: "On the face of it this appeared to be a statement from an independent witness, somebody who is not a close friend of either of the two people, somebody who said in terms that she held them in the same regard, somebody who was a neighbour to Ms Pryce who had been turned to in a moment of crisis but who otherwise was not close to her.
"Ms Briscoe presented herself, as you will see from her statements, as somebody who was quite independent and objective in her evidence, rather than someone who was involved with the media and who it appears was quite intent on Mr Huhne's downfall herself."
Emails obtained during the Huhne-Pryce trial showed she had advised Ms Pryce about a contract with the Sunday Times, and was involved in speaking to the Mail on Sunday about the story.
When Ms Briscoe was later interviewed by police following her arrest, she pointed out an additional letter "I" in her statement, claiming it changed the meaning, the court was told.
The prosecution alleges this change was an attempt to bolster a denial by her that she had not had contact with the Mail on Sunday and she had altered that document, whether it helped her case or not.
Former Energy Secretary Mr Huhne was jailed in March along with his ex-wife Ms Pryce, after she took speeding points for him in 2003. Both have since been released from prison.
Ms Briscoe, who is also a barrister, has been suspended since her arrest in October 2012.
The trial continues.