Within a day of reporting his pregnant wife missing, Scott Peterson lied about his extramarital affair, gave conflicting accounts of his whereabouts and brushed off in-laws helping search for Laci Peterson, prosecutors said Tuesday in opening arguments of Peterson's murder trial.

Prosecutor Rick Distaso wants jurors to connect those dots, along with other circumstantial evidence, and conclude that Peterson killed his wife.

Peterson, 31, could face the death penalty or a life sentence without parole if convicted in a trial that is expected to last up to six months.

From the moment Peterson called his mother-in-law on Christmas Eve 2002 and said he had returned from a fishing trip to an empty house, things did not make sense, Distaso said.

"He says, 'Mom, Laci's missing,' " Distaso told jurors. "Right then, Sharon Rocha knew that things were very seriously wrong."

By nightfall, family members had joined police to investigate the missing-person report. Their search first focused on a park near the couple's Modesto home, where Laci Peterson, eight months pregnant, used to walk the family's golden retriever before a doctor recommended that she stop because of recurring dizziness.

In the park, a panicked Rocha rifled through garbage cans in the fog-shrouded evening.

When she saw Scott Peterson, she asked, " 'What's going on? Where were you fishing?' " Distaso said. After giving Rocha "one-word responses," Peterson wandered off, the prosecutor said.

Distaso ticked off what he implied was a series of lies told by Peterson.

Peterson told Rocha that he had been fishing on San Francisco Bay, but later told Laci Peterson's uncle and two neighbors that he had been playing golf all day. He was also unable to tell police what he had been trying to catch on his fishing trip.

He told investigators that he never had an affair -- a lie that would become public once his mistress, massage therapist Amber Frey, stepped forward.

By Christmas Day, Peterson was more engaged -- and talking in ways that Distaso suggested point to his guilt. He called police, for example, to ask whether they were using cadaver-sniffing dogs to search the park.

" 'We haven't come to the conclusion yet that Laci Peterson is dead,' " Distaso said the officer told Peterson. "That kind of sets the stage for this entire case."

Defense attorney Mark Geragos has countered that the authorities unfairly targeted Peterson from the start and ignored important leads that did not fit their theory.

Sharon Rocha and Ron Grantski, the mother and stepfather of Laci Peterson, leave the courthouse in Redwood City, Calif., where opening arguments were heard in the murder trial of Laci Peterson's husband.Lee and Jackie Peterson, the parents of murder suspect Scott Peterson, walk into the courthouse. Their son is accused of killing his pregnant wife, Laci, and their unborn son.