He was found guilty of second-degree murder in the slaying of the couple's unborn child, Conner.
First-degree convictions (which means the murders were premeditated) carry the death penalty or life without parole. Second-degree murder convictions do not require a finding of premeditation and carry sentences of 15 years to life for each count.
It was said by those in the courtroom that Laci's family burst into tears at the verdict, while Scott Peterson showed no emotion.
Earlier Friday, Judge Alfred A. Delucchi announced that the jury had reached its decision, with the outcome to be announced at 1 p.m. California time. The actual verdict was heard at 4:10 p.m., and the emotion inside and outside the courthouse was said to be palpable.
The jury will return to court Nov. 22 to begin the four-day penalty phase of the trial, said the judge, who warned the jurors not to discuss the case with the media or each other.
Deliberations in the case had resumed Friday morning (after the jury took off for Veterans Day) and only one workday after a second juror on the six-man, six-woman panel had been replaced.
On Wednesday, without public explanation, Delucchi dismissed the foreman, Gregory Jackson, a man in his mid-40s who has medical and law degrees. The alternate who replaced him was a man whose future son-in-law now owns a restaurant that Scott and Laci Peterson once owned in San Luis Obispo. (That coincidence was deemed not to be a conflict of interest.)
Prosecutors claimed former fertilizer salesman Peterson, 31, who was having an affair with massage therapist Amber Frey, killed his pregnant wife Laci in their Modesto, Calif., home on or around Dec. 24, 2002, then dumped her weighted body into San Francisco Bay. Her disappearance quickly made national headlines.
The remains of Laci and the fetus, a boy the couple had planned to name Conner, were discovered in mid-April 2003 a few miles from where Peterson says he went fishing alone the day his wife vanished. At the time of his arrest, Peterson had died his hair blond and was near the California-Mexico border.
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Stanislaus County prosecutor, Rick Distaso, on the other hand, was hindered in his arguments by what was considered a lack of tangible evidence, though he repeatedly painted Peterson as a liar and a cheat.