WASHINGTON – After the judge dismissed one of its members, the jury finished a fourth day of deliberations Monday without a verdict in the perjury trial of former White House aide I. Lewis “Scooter” Libby.

Most of the morning was consumed by deciding what to do about an art historian on the jury who saw or read something over the weekend about the trial. After interviewing her in private along with lawyers in the case, U.S. District Judge Reggie B. Walton ruled that “what she had exposure to obviously disqualifies her.”

The judge let the jurors continue deliberating with just 11 members after the defense endorsed that option. He overruled prosecutors who asked him to seat one of two alternate jurors who heard the trial and remain on standby.

Walton said he didn’t want to “throw away two and a half days” of discussions the jury has had since getting the case at midday last Wednesday. If an alternate had been seated, the jury would have been required to begin its deliberations over from the beginning.

The jury returns Tuesday.

Libby, who was chief of staff to Vice President Dick Cheney, is accused of obstructing the investigation into the 2003 leak of the identity of CIA operative Valerie Plame, whose husband was a prominent Iraq war critic.

Walton never disclosed what the juror had seen, but he concluded the exposure was not intentional and resulted from a misunderstanding of his orders. He has ordered jurors to avoid media coverage of the case and to stay off the Internet.

The dismissed juror formerly served as a curator of prints at the Metropolitan Museum of Art in New York. She was also the only juror who did not wear a red T-shirt as part of the jury’s Valentine’s Day greeting to the court.

Usually defense attorneys want the largest number of jurors available because they only need one to hold out against conviction in order to force a mistrial, said Lawrence Barcella, a prominent Washington defense attorney. “This is surely a well thought out calculation for the defense based on the jurors they have, the way they guess the deliberations might be going, and who the alternate would be.”

Ultimately, however, decisions like this are “guesswork, tempered by the experience and instincts of very experienced attorneys who have demonstrated good instincts,” Barcella said.

Associated Press writer Matt Apuzzo contributed to this report.