The judge overseeing the Scott Peterson murder trial replaced a juror with an alternate Tuesday and cautioned the new panel not to consider any evidence other than what was presented in the trial.

After five days of deliberations, Judge Alfred A. Delucchi told jurors that they must restart discussions.

The order caused a frenzy among spectators at the small-town courthouse where many had expected the day to bring a verdict -- or, possibly, the announcement of a deadlocked jury -- in the case of the fertilizer salesman accused of killing his pregnant wife, Laci, and their unborn child nearly two years ago.

Delucchi did not explain why he replaced the juror, a woman in her fifties of Hawaiian descent who is a retiree from a local utility company. Some media organizations cited sources who said the woman had apparently been caught doing independent research in the case -- an offense that could have included actions as varied as visiting a crime scene, reading a newspaper or discussing the case outside the jury deliberation room.

The juror, who has been placed under a gag order, had drawn relatively little scrutiny from the cable TV commentators who have been closely chronicling the trial since it began eight months ago because she showed little expression during testimony. During jury selection, she described herself as a "crusader" who would not back down if she disagreed with other jurors.

In her place, Delucchi appointed an alternate juror described as a mother of four in her late twenties or early thirties who, in contrast, has drawn plentiful attention for her tattoos, deep-red hair and shows of emotion -- smiling at defense attorney Mark Geragos's jokes, weeping when prosecutors showed autopsy photos of Laci Peterson and her unborn son.

Spectators who managed to snag some of the few seats in the crowded courtroom said jurors appeared grim as they received the news. The foreman, both a doctor and a lawyer, was reportedly red in the face.

"They're in a difficult position," said Chuck Smith, a local former prosecutor who has followed the case closely. "I'm sure there is some frustration that all this work they've done over the last five days is being literally thrown out the window and they have to start all over."

The Christmas Eve 2002 disappearance of Laci Peterson, 27 years old and eight months pregnant, drew television news audiences into a tragedy that deepened amid disclosures of her husband's affair with a massage therapist who believed he was single. Scott Peterson told police that he returned from a fishing trip that day to find his wife missing. After the body of Laci and their near-term son washed up in San Francisco Bay months later, Peterson was charged with two counts of first-degree murder. He could face the death penalty if convicted.

On Monday, defense attorneys asked for a mistrial after jurors examining Peterson's boat climbed in and rocked it back and forth -- an action that the defense said amounted to an unlawful use of evidence to conduct an experiment. While prosecutors say that Peterson threw his wife's body from the boat, defense attorneys have argued that it would have been impossible for him to do so without capsizing. The judge denied the request.

Argetsinger reported from Los Angeles.

Judge Alfred A. Delucchi did not explain why he dismissed a juror in the months-long murder trial.