Yesterday, a jury of eight women and four men began weighing a month of testimony from 19 witnesses in a case that began as a probe into the outing of former Central Intelligence Agency operative Valerie Plame and three years later ended up focusing on the trustworthiness of recall and the semantics of lying.

In court, Special Prosecutor Patrick Fitzgerald told jurors that Mr. Libby deliberately lied to Federal Bureau of Investigation agents and a grand jury to try to cover up the administration's efforts to respond to criticism of the Iraq war.

In response, Mr. Libby's attorneys highlighted "mis-recollections" by a number of prosecution witness, including several reporters, to bolster their argument that Mr. Libby didn't lie but simply had faulty memory when he made erroneous statements to investigators.

The roots of the Libby case lie in a debate over use of intelligence in the buildup to the Iraq war. It began when Ms. Plame's husband, former U.S. Ambassador Joseph Wilson, complained publicly that the Bush administration had misused or ignored intelligence he gathered that cast doubt on Iraq's alleged efforts to obtain weapons of mass destruction.

Mr. Wilson in July 2003 went public with his story of taking a CIA sponsored trip to Africa to check out claims of connections to Iraq's weapons program. In interviews and in an opinion article, he called into question Mr. Bush's use of since-discredited intelligence that alleged Iraq sought weapons materials in the African nation of Niger. In retaliation, prosecutors say, Mr. Libby and other officials sought to disclose Ms. Plame's identity to reporters, making the argument that her intelligence job was the only reason Mr. Wilson looked into Iraq's weapons efforts in the first place.

The administration subsequently backed off the Niger claim. However, Mr. Libby told the grand jury in the case that he continued trying to leak selective portions of intelligence reports to journalists in order to portray the Niger-Iraq link as true, under orders from Mr. Cheney. Administration officials complain that Mr. Wilson was the one misusing his role in the intelligence process by talking publicly about his findings.

In any case, the trial has provided congressional intelligence officials with extensive information on how the vice president's office functioned semi-autonomously in pushing foreign-policy initiatives. These officials said the information could prove helpful in continuing investigations into how public statements made by the president and vice president differed from the underlying intelligence provided by the CIA and other intelligence agencies.

Richard Ben-Veniste, former Democratic counsel to the Senate Whitewater Committee and head of the Watergate special prosecutor's office, says the trial has served "to reveal the inner workings of the vice president's office, and particularly the willingness to declassify information to assist in the damage control effort that appeared to be entirely political in nature."

Meanwhile, the Pentagon report said that as Mr. Feith assembled his intelligence reports -- highlighting, in particular, alleged links between Iraq and al Qaeda terrorists -- his office briefed four key officials, Mr. Libby among them. The report said the Pentagon office presented its findings to the White House as a conclusive intelligence assessment, though the CIA strongly opposed those findings.

Mr. Feith has complained bitterly that the report, and the congressional response to it, distorts what was a legitimate effort to raise questions about intelligence conclusions, not to distort them.

The latest controversies come as the administration faces challenges from foreign governments and U.S. lawmakers skeptical of its recent claims that Tehran is supplying Shiite militias in Iraq with munitions and arms. Critics accuse the White House of mimicking the tactics used in building the case for war against Iraq in 2002 and 2003.

Administration officials voice exasperation over the response, saying U.S. intelligence agencies have developed extensive evidence of Iran's involvement in Iraq. They also say that changes in the intelligence community since the Iraq war have significantly improved U.S. intelligence.

"It's frustrating for the entire process," says one intelligence official working on Iran. "The whole message is being challenged.