Jurors return Friday to deliberate Peterson's fate
Prosecutor calls him 'the worst kind of monster'
Scott Peterson during defense closing arguments in the penalty phase of his murder trial on Thursday.
Jurors to resume deliberations in Peterson case.
Scott Peterson's mother pleads for her son's life.
The Peterson sentencing phase enters its second week.
REDWOOD CITY, California (CNN) -- A six-man, six-woman jury began deciding Thursday whether Scott Peterson, convicted of killing his pregnant wife and unborn son nearly two years ago, should die or spend the rest of his life in prison.
Jurors received the case about 2 p.m. (5 p.m. ET), after instructions from San Mateo County Superior Court Judge Alfred Delucchi and closing arguments from attorneys. About two hours later, the jury was dismissed for the night without reaching a decision.
Deliberations are to resume Friday at 8 a.m. (11 a.m. ET).
Peterson, 32, will be sentenced to either the death penalty or life in prison without parole.
On November 12, the same jury convicted Peterson of first-degree murder in the death of his 27-year-old wife, Laci, and second-degree murder, punishable by 15 years to life in prison, in the death of the couple's unborn son, Conner. (Full story)
Jurors agreed with prosecutors' contention that Peterson strangled or smothered Laci and dumped her body into San Francisco Bay. She was reported missing on Christmas Eve 2002. (Timeline)
Jurors, who are sequestered during deliberations, must reach a unanimous verdict to recommend that Peterson be sentenced to death.
At formal sentencing, set for February 25, Delucchi may override a recommendation of death and sentence Peterson to life in prison without parole, but cannot override a decision of life in prison without parole.
Calling Peterson "the worst kind of monster," prosecutor David Harris urged jurors Thursday to recommend that Peterson die for killing his wife.
Peterson's attorneys begged jurors to spare his life.
"Nobody feels ... that if Scott Peterson was a good golfer, that if Scott Peterson was a Cub Scout, that eases the murder of Laci and Conner," defense attorney Mark Geragos said.
"As I indicated to you, I'm not second-guessing any of your decisions. What we're saying is, that this is a life that has value."
Defense attorney Pat Harris told the jury Peterson "has a lot of good in him" and would be a good candidate to help others in prison.
"There's an opportunity to make something out of a life that has essentially gone wrong, a chance to see that others benefit from the positive part of Scott Peterson, some chance for him to do some good for the rest of his life," Harris said.
Prosecutors said the motive was Peterson's desire to live life as a freewheeling bachelor, unencumbered by a wife and child.
During the trial, jurors heard hours of taped telephone conversations between Peterson and his mistress, massage therapist Amber Frey.
During the penalty phase, Peterson's friends and relatives took the stand to plead for his life, calling him a kind person who could benefit others in prison.
Peterson's mother cried on the stand Wednesday as she begged jurors to spare her son's life.
"We would lose a whole family," Jackie Peterson testified. It "would be like they never existed ... such a waste, irreversible."
Prosecutor David Harris urged jurors to reject the argument that life in prison without parole would be worse punishment than death.
"If you have life, he gets to sit in a cell, read a book, write letters; he gets to have life," he said. "All the things that Laci and Conner would love to do, all the things that Laci's family would love to be able to share with Laci and Conner."
He noted that while others were praying for the safe return of Laci and her baby, "the man who knew where they were laughed and lied. ... He is the worst kind of monster."
California law prohibits jurors from considering the emotional effect on defendants' families when deciding on a sentence, and Delucchi instructed jurors not to allow sympathy to be a factor.
CNN's Rusty Dornin contributed to this report.