that the note was an effort to persuade Ms. Miller to lie to the grand jury and back up Mr. Libby’s story, saying it demonstrated Mr. Libby’s “consciousness of guilt.”

Former Times Reporter Testimony Is Challenged

WASHINGTON, Jan. 31 — A former reporter for The New York Times jousted for nearly two hours on Wednesday with a lawyer for I. Lewis Libby Jr. over her credibility and memory.

They argued over the significantly damaging testimony that the reporter, Judith Miller, had given about three conversations she had with Mr. Libby, the former chief of staff for Vice President Dick Cheney, who is facing perjury and obstruction of justice charges.

Ms. Miller testified on Tuesday that Mr. Libby had told her in those conversations details about the identity of Valerie Wilson, a Central Intelligence Agency operative, days before Mr. Libby said he learned about Ms. Wilson from reporters.

William H. Jeffress Jr., the lawyer for Mr. Libby, asked Ms. Miller what other officials she had spoken with about Ms. Wilson.

“I remember having conversations, sir,” she said, casting quick glances at the jury and at her lawyers sitting in the back of the courtroom. But she said she could not remember talking to anybody else about Ms. Wilson, who is also known by her maiden name, Valerie Plame.

Mr. Jeffress then showed a video clip of a television interview with Ms. Miller from Jan. 8, 2006. In the clip, she said she had discussions with “senior government officials and some not-so-senior government officials” about Ms. Wilson and her husband, Joseph C. Wilson IV, who wrote an op-ed article, published July 6, 2003, in The New York Times, accusing the Bush administration of distorting intelligence about Iraq’s efforts to buy uranium in Africa to bolster the case for going to war.

Mr. Jeffress also cited an affidavit making a similar assertion that Ms. Miller filed with the court before she went to jail for 85 days after initially refusing to testify before a grand jury.

“Who were these senior government officials?” Mr. Jeffress asked.

Ms. Miller replied, “I was not talking about Joe Wilson,” adding, “I was using Joe Wilson as a shorthand” for questions about whether Iraq had tried to buy uranium in Africa.

Mr. Libby is charged with lying to a grand jury and to F.B.I. agents who were investigating the leak of Ms. Wilson’s name to reporters.

Pressed by Mr. Jeffress about the conflict between her testimony on Wednesday and the interview and the affidavit, Ms. Miller, who was combative and testy at times, replied: “I don’t know what you want me to say beyond what I’ve said. I don’t remember the people I talked to” about the Wilsons.

“That’s all I can tell you, sir,” she added.

Asked again about such conversations, she said with exasperation: “I just don’t remember,” then added in a loud voice, “I don’t remember.”

After Mr. Jeffress concluded his questioning, Ms. Miller regained her composure as she answered more questions, which came from the jury because Judge Reggie M. Walton had allowed jurors to submit written questions.

One juror wanted to know why Ms. Miller had chosen to go to jail. She said it was because of her deeply held principles that journalists should be allowed to protect their sources in order to report on issues government officials hoped to conceal.

She was followed to the witness stand by Matthew Cooper, a former Time magazine reporter who, unlike Ms. Miller, avoided going to jail by agreeing earlier to testify to the grand jury.

Mr. Cooper testified Wednesday that Mr. Libby discussed Ms. Wilson during a telephone interview on July 12. He also recounted how he first learned about Ms. Wilson on July 11 from Karl Rove, the president’s chief political strategist.

He said that Mr. Rove told him to be wary of Mr. Wilson’s criticisms in The Times. “Don’t go too far out on Wilson,” Mr. Cooper recalled Mr. Rove saying, warning him that Ms. Wilson worked at “the agency.”

Mr. Cooper testified that when he spoke to Libby, he had heard that Mr. Wilson’s wife worked at the C.I.A. He said that Mr. Libby responded, “I heard that too.”

The trial hinges largely on whether the jury believes the prosecution account that Mr. Libby lied when he contended he learned of Ms. Wilson’s identity from reporters and not from fellow administration officials.

The first six witnesses, present or former government officials, have testified that they had informed Mr. Libby about Ms. Wilson. The two reporters, Ms. Miller and Mr. Cooper, testified that Mr. Libby discussed the information with them.

Mr. Libby’s defense is that many of the witnesses do not correctly remember what occurred. In addition, his lawyers are trying to make the case that if Mr. Libby gave inaccurate information to the grand jury and to investigators, it was merely a case of faulty memory.

Patrick J. Fitzgerald, the chief prosecutor, said Wednesday he wanted to introduce evidence to explore one of the case’s most intriguing mysteries: a note from Mr. Libby to Ms. Miller giving her permission to testify.

In the September 2005 note, Mr. Libby told Ms. Miller, who was in jail at the time, that she was no longer bound by her pledge of confidentiality and that she should testify before the grand jury. He added, cryptically, that the aspen trees in Colorado change color at the same time because they are bound at the roots.

Mr. Fitzgerald said Wednesday, while conferring with the judge while the jury was out of the room, that the note was an effort to persuade Ms. Miller to lie to the grand jury and back up Mr. Libby’s story, saying it demonstrated Mr. Libby’s “consciousness of guilt.”

Judge Walton pointed out that Ms. Miller’s testimony had not helped Mr. Libby, however, and had contributed to the indictment against him.

“We don’t think that the letter worked,” Mr. Fitzgerald said. “He told her what he wanted her to say.”

Judge Walton deferred a decision on whether and when Mr. Fitzgerald could introduce the note to the jury.

Mr. Fitzgerald said he hoped to complete the prosecution’s case by early next week, perhaps on Monday.

Two jurors from the original panel of 16 have had to be excused, meaning that if another 3 jurors leave, it would raise the likelihood of a mistrial. Judge Walton asked the jurors on Wednesday to please remain in good health.

Defense lawyers said Wednesday they had subpoenaed Jill Abramson, the managing editor of The Times, to appear as a witness. Ms. Miller testified Tuesday that she had a conversation with Ms. Abramson in July 2003 in which she suggested assigning someone to report on the issue of Mr. Wilson’s report and what role, if any, Ms. Wilson played in sending him on the assignment to Africa.

Ms. Abramson has denied that account in an article published in The Times. The article examined Ms. Miller’s behavior in the Libby story as well as her pre-war reporting that intelligence officials believed Iraq had amassed a stockpile of weapons of mass destruction.