A jury found Scott Peterson guilty Friday of killing his pregnant wife, Laci, and their unborn child in the saga of suburban adultery and betrayal that transfixed much of the nation for nearly two years.

Peterson, a 32-year-old fertilizer salesman from Modesto, showed no emotion, staring stonily at the jury box as the foreman announced a finding of first-degree murder in the death of Laci and second-degree murder in the death of their near-term son, whom the couple had named Conner. Laci Peterson's parents wept in their courtroom seats, while outside the building, hundreds of onlookers cheered and pumped their fists when word of the verdict emerged.

The jury will reconvene Nov. 22 to decide whether to sentence Peterson to life in prison or give him the death penalty.

The verdict's arrival early Friday afternoon surprised the throngs of courthouse observers and media commentators who had expected more protracted deliberations after five months of testimony and a tumultuous week in which two jurors were replaced.

Prosecutors had portrayed Peterson as a selfish narcissist who they said killed his wife and dumped her weighted body into San Francisco Bay to escape a lackluster marriage and the impending pressures of fatherhood. They focused much of their testimony on Peterson's patterns of deceit, noting his affair with a Fresno massage therapist who believed he was single and the conflicting stories he gave police and relatives after his wife's disappearance.

Defense attorneys, meanwhile, suggested Laci was a victim of random violence and Scott the victim of a frame-up.

The reconstituted jury spent only a few hours deliberating after returning from a Veterans Day holiday before announcing it had reached a conclusion. The two alternates added to the panel had not been part of the deliberations.

"What the first-degree murder means is that the jury completely accepted the prosecution theory and completely rejected the defense theory," said Paula Canny, a former prosecutor who followed the trial.

She predicted the defense would face long odds in the sentencing. "These 12 people hate Scott Peterson," she said.

California's last execution was in January 2002, when Stephen Wayne Anderson was put to death by lethal injection for the 1980 murder of an 81-year-old retired piano teacher during a burglary.

About 1,200 women are killed in the United States each year by their husbands or boyfriends. None in recent years has drawn as much attention as Laci -- an attractive 27-year-old brunette whose disappearance on Christmas Eve 2002, just a month before her baby was due, triggered national media coverage, particularly on cable news stations.

What began as a missing-woman story evolved into a full-blown soap opera as rumors of Scott Peterson's infidelity were picked up by supermarket tabloids. Peterson gave a tearful interview to ABC's Diane Sawyer, claiming his wife knew about his affair and that they were working out their problems.

"It wasn't anything that would break us apart," he said.

Three months later, the remains of Laci and the fetus washed ashore near the spot, about 90 miles from their home, where Peterson had told police he had gone fishing the day his wife vanished.

The bodies were so badly decomposed that the coroner could not determine the cause of death.

Peterson was arrested days later just north of the Mexican border. His hair and goatee had been dyed blond. He was carrying nearly $15,000 in cash.

More than 800 reporters were credentialed to cover the trial, which began with jury selection in February. Court TV preempted regular programming to provide nonstop coverage of closing arguments and the verdict -- a first for the network in a case without cameras in the courtroom. Tabloid and national entertainment magazines have seen huge increases in copies sold when stories on the Peterson case were featured.

The days since closing arguments last week had provided even more drama for court watchers. On Tuesday, a woman was removed from the jury for reportedly conducting independent research on the case. On Wednesday, Judge Alfred A. Delucchi removed the foreman, a doctor and lawyer who kept more than a dozen notebooks of observations throughout the trial. The reason for his dismissal has not been made public.

Meanwhile, a circus atmosphere took hold outside the small-town courthouse, as hundreds of people obsessed with the trial arrived. A replica of Peterson's boat, left in a nearby parking lot by defense attorney Mark Geragos, turned into a makeshift shrine where visitors left candles and letters for Laci.

Throngs of people rushed to the courthouse as word that a verdict had been reached spread through the town. Customers of one grocery store down the street from the courthouse spread the news to clerks and bag boys. Bank employees asked to close up shop for just a moment to hear the verdict read.

"I wasn't this nervous for my first grandchild," one courthouse employee said.

Helicopters hovered overhead as television satellite trucks crammed the courthouse parking lot. Hundreds of reporters milled around the courtyard to catch a glimpse of the families arriving.

"We didn't expect this today, did we?" said Evelyn Winnegar, 64, a retired secretary from Redwood City who waited for the courtroom seat she had won in a public lottery. "I was getting so worried about a hung jury, I thought we were going to have to go through this all over again."

As she waited, Winnegar pointed out the key courtroom players to others in line, referring to them by first name, as though they were neighbors.

Peterson arrived in a blue suit and salmon-colored tie, seemingly in a good mood. He smiled and spoke animatedly to the court staff and his lawyers, then mouthed a greeting to his family in the front row. His mother, Jackie, entered the room smiling, as well.

Geragos was not present, apparently having been detained out of town on other business on a day no verdict was expected.

As the verdict was read, loud gasps pierced the courtroom. Peterson and his mother, though, showed blank faces. On the other side of the room, Laci's mother, Sharon Rocha, burst into loud sobs. Her brother, Brent, nodded his head and wiped tears from his face.

Prosecutors Rick Distaso and Birgit Fladager left the courtroom to applause from people gathered in the hallway after Delucchi thanked the six-man, six-woman jury for their service.

Argetsinger reported from Los Angeles.

Scott Peterson, 32, admitted an affair.Gloria Allred, an attorney for Amber Frey, Peterson's admitted mistress, leaves the Redwood City, Calif., courthouse yesterday after Peterson was found guilty of murdering his wife and unborn son.