WASHINGTON — Targeting a lengthy memory lapse, lawyers for I. Lewis “Scooter” Libby Jr. are attacking the credibility of a former New York Times reporter who testified yesterday that the one-time vice presidential aide told her the identity of a CIA officer weeks before he claims he first learned the agent’s name.

The reporter, Judith Miller, testified that Mr. Libby, who is on trial here for perjury, told her at a meeting on June 23, 2003, that the wife of a former American ambassador, Joseph Wilson IV, worked for the CIA. Mr. Libby was then Vice President Cheney’s chief of staff, and he has told a grand jury that he did not learn that information until he spoke to reporters after Mr. Wilson published an opinion piece criticizing the Bush administration the following month. Ms. Miller is one of several witnesses in the trial so far who have contradicted Mr. Libby’s account. The defense quickly sought to undermine Ms. Miller’s testimony, questioning her aggressively on the point that for more than a year, she had forgotten that the June 23 meeting with Mr. Libby ever took place. Ms. Miller drew national attention in 2005 when she served 85 days in jail for refusing to disclose her confidential sources before a grand jury investigating the outing of the CIA officer, Valerie Plame.

Her court appearance yesterday brought her face to face with the prosecutor who had her put in jail, Patrick Fitzgerald. The First Amendment debate crept back into the proceeding yesterday, but with a distinct twist: This time it was Mr. Fitzgerald who objected to Ms. Miller’s having to answer questions about sources other than Mr. Libby, who granted her a waiver to testify about their conversations. Ms. Miller said she could not remember the names of other people with whom she discussed Ms. Plame, and the defense sought to press her for other sources in an effort to damage her credibility.

In an argument that interrupted the trial several times, Mr. Fitzgerald said the questions were irrelevant and a “fishing expedition,” a position that Judge Reggie Walton said he was leaning toward accepting. He will rule this morning before Ms. Miller returns to the witness stand.

Ms. Miller yesterday described Mr. Libby as “agitated and frustrated and angry” during the June 23 meeting and said he complained that the CIA was engaging in a “perverted war of leaks” about intelligence leading up to the war in Iraq. The meeting came just more than two weeks before the White House was forced to retract 16 words from President Bush’s State of the Union address in which he said Iraq had been trying to purchase yellowcake uranium from Niger. Mr. Wilson’s opinion piece on July 6 countering the claim had preceded the retraction, and Ms. Miller testified that Mr. Libby mentioned that Ms. Plame worked for the CIA in two subsequent meetings after the op-ed appeared.

In cross-examination, a defense attorney, William Jeffress Jr., took aim at Ms. Miller’s faulty recollection in which she testified that she did not remember the first meeting with Mr. Libby until finding a notebook in her New York office — after she testified before the grand jury in October 2005. The notebook contained details that jogged her memory of the encounter, Ms. Miller said; she notified Mr. Fitzgerald and returned for more questioning that led to an account that further contradicted Mr. Libby’s sworn statements.

Mr. Jeffress’s line of inquiry suggested disbelief that Ms. Miller could forget an entire encounter through months of court battles and 12 weeks sitting in a Virginia jail cell.

“Do you have a good memory?” he asked.

“About some things,” Ms. Miller replied. At another point, she said, “It was a tumultuous period.”

Mr. Jeffress pressed Ms. Miller about whether she had an actual memory of the meeting or whether she was relying solely on her notes. While saying at one point that her memory was “generally note driven,” she testified to an actual recollection of the June 23 meeting with Mr. Libby.

The defense has been attacking the memory of witnesses repeatedly during the trial, a strategy that could lead into its argument that Mr. Libby was simply too busy handling matters of state to recall details of conversations he had with reporters about Ms. Plame. Earlier yesterday, Mr. Cheney’s former counsel and current chief of staff, David Addington, testified that Mr. Libby told him in September 2003, “I didn’t do it,” in reference to the CIA leak investigation that was just beginning. He didn’t specify was “it” was. Mr. Libby is not charged with the leak, but in lying under oath about conversations he had with reporters.