Former White House aide I. Lewis"Scooter"Libby wants a memory expert to explain how he _ and prosecution witnesses _ may have different recollections of their conversations about a CIA officer's identity.

In a court filing Monday, defense lawyers said Libby has a right to present testimony from Robert A. Bjork, chairman of the psychology department at the University of California at Los Angeles, to correct misperceptions that jurors may have about the reliability of memory.

Libby, Vice President Dick Cheney's former chief of staff, faces trial in January for lying to FBI agents and a federal grand jury about how he learned and what he subsequently told reporters about then-CIA officer Valerie Plame in 2003.

The crux of Libby's defense will be that he was too preoccupied with national security"matters of life and death"and that he could have easily confused"snippets of conversations"he had with reporters from Time magazine, NBC and the New York Times.

The court filing confirms that Libby's lawyers want to try to force a jury into deciding whose memories of those conversations are accurate _ Libby's or the three reporters.

But the defense team will have to convince U.S. District Judge Reggie B. Walton, who in a hearing earlier this year voiced skepticism about the relevance of testimony about memories.

Plame's identity as a CIA officer was revealed in a July 14, 2003, article by syndicated columnist Robert Novak. At the time, Plame's job as an operations officer for the spy agency was classified information.

Novak's column appeared eight days after Plame's husband, former U.S. Ambassador Joseph Wilson alleged in an opinion piece in The New York Times that the Bush administration had twisted prewar intelligence on Iraq to justify going to war.

In their court filing, Libby's lawyers cited studies _ including a recent survey of District of Columbia jurors _ that they said show the misconceptions jurors have about the reliability of witnesses'recollections.

They said Bjork can explain that contrary to what most jurors think,"memory does not function like a tape recorder, with memories recorded, stored and played back verbatim."

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