An 11-member jury is deliberating the fate of I. Lewis Libby Jr. after the judge removed one of the jurors yesterday because of information she learned out of court about the case against the former chief of staff to Vice President Cheney.

Judge Reggie Walton did not announce publicly just what the juror had seen, read, or heard, but, according to the Associated Press, he declared that “what she had exposure to obviously disqualifies her.”

Prosecutors asked the judge to replace the juror with one of two alternates, while defense attorneys said they preferred to go forward with the jury one short of the usual federal court complement of 12.

The reasons for the differing stances of the two sides were not clear, but some observers said the body language of one of the alternates was chilly during the defense’s closing arguments.

The woman who was removed was identified during the jury selection process as a former curator of prints at the Metropolitan Museum of Art. She was the only one who did not take part when the rest of the jury donned red T-shirts emblazoned with hearts on Valentine’s Day in a tribute to the court staff.

Today will mark the fifth day of jury deliberations in Mr. Libby’s obstruction-of-justice and perjury trial, which lasted about four weeks before going to the jury last Wednesday. If an alternate were added to the panel, the judge would be required to instruct jurors to begin their deliberations again.

Some defense tactics in the case appeared to be aimed at prompting one or two jurors to hold out for Mr. Libby’s acquittal, effectively forcing a mistrial. That sort of a mistrial would be seen as a victory for the defense, as it seems unlikely that prosecutors would seek to retry the former White House aide under those circumstances. On the other hand, a mistrial caused by jurors being exposed to press coverage would say nothing about the persuasiveness of the prosecution’s case. Under that scenario, a retrial would be a more likely possibility.