Defense lawyer Mark Geragos made the request in a motion filed Wednesday in San Mateo County Superior Court. The details will not be made public until after Judge Alfred A. Delucchi reviews the file before the scheduled start of the penalty phase Monday morning, which could now be delayed.
The motion marks the second time Geragos has sought to have two juries seated for the trial, one for the guilt phase and one to determine the penalty.
In the first request, filed in February, Geragos contended that "the vast adverse publicity, the abnormally high prejudging of guilt and the strong statistical showings that a death-qualified jury tilts in the favor of the prosecution" supported his request.
The judge denied that motion and let the trial move forward with just one jury.
Peterson, 32, wasin the death of Laci Peterson and of second-degree murder in the death of the fetus. The jury also agreed on a "special circumstance" that calls for capital punishment; namely that he killed another person, the fetus, during the premeditated killing of his wife.
Laci Peterson vanished just before Christmas 2002; her remains and that of the male fetus turned up on the shore of San Francisco Bay four months later.
The case was moved from Modesto after a judge there found Peterson couldn't get a fair trial in the couple's hometown. Redwood City, where the five-month trial was held, is 90 miles away.
The jurors who convicted Peterson on Friday were sequestered during deliberations but were sent home pending the start of the penalty phase.
If the judge turns aside the defense request for a separate penalty phase jury, the old panel will resume next week by hearing testimony on exacerbating and mitigating factors to be weighed to determine punishment. The penalty phase is expected to take several days, and jurors are to be sequestered once again during deliberations.
Analysts said Peterson himself is unlikely to take the stand and beg for mercy; doing that would require him to admit to the murders, and throw away any chance of overturning the convictions on appeal.
"The presumption of innocence now is gone sowith a description of how heinous the crime was and defense attorneys essentially begging the jury for mercy," said CBS News Legal Analyst Andrew Cohen.
What's more, Cohen says, "(Defense lawyers) were telling jurors themselves that their client was a liar and a cheat and a no-good sort of guy, and now they have to turn around and say, 'Wait a minute; even though he's all those bad things, he still deserves a break."'
The verdicts came after a little more than seven hours of deliberation by the final 12 jurors, following a five-month trial and a chaotic final week. The judge removed two jurors for reasons that have not been publicly disclosed.
"Kicking someone off the jury is one of the riskiest things you can do in a trial. On appeal, the court will look at that very carefully, very carefully," said Jim Hammer, a former San Francisco prosecutor who has been observing the case. "Two jurors in two days? I've never heard of that happening before."