Special Prosecutor Patrick Fitzgerald took on the first witness in the CIA leak case Thursday, dissecting an expert witness until she acknowledged errors and misstatements in her research.

Vice President Dick Cheney's former chief of staff, I. Lewis "Scooter" Libby, hoped the hearing would persuade a judge to let him call a memory expert at his obstruction and perjury trial in January.

At the outset of the procedural hearing, U.S. District Judge Reggie Walton indicated that he was not inclined to allow a memory expert to testify at the trial. Still, he allowed Libby's lawyers to present a witness to bolster their claim that memory experts would help in his defense.

When it came Fitzgerald's turn, the veteran prosecutor launched into a nearly three-hour cross-examination of the witness — psychologist Elizabeth Loftus — that had some members of the audience shaking their heads.

It was the first public courtroom confrontation between Fitzgerald and Libby's defense team and foreshadowed a contentious trial.

Libby wants to use a memory expert to help argue that, when he made false statements to investigators about his conversations with reporters regarding Central Intelligence Agency operative Valerie Plame, it was because of faulty memory. Prosecutors say he lied.

Loftus testified that many jurors do not understand how memory works and how unreliable it can be.

Fitzgerald challenged the validity of memory research. Citing footnotes in her publications, presenting conflicting statements and questioning her methodology, Fitzgerald got Loftus to acknowledge that a statement in one of her research papers was taken out of context and that a figure in one of her books was incorrect.

Libby's defense team had no comment after court.

Walton did not immediately rule on whether to allow the memory testimony at trial. He closed the courtroom to continue the debate over how much classified information Libby should be allowed to present at trial.

Libby is the only person charged in the leak case. Plame believes the Bush administration leaked her name to reporters as retribution for her husband's criticism of prewar intelligence on Iraq.