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

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

Peterson, 31, could face the death penalty or life 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 didn't 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 had joined police to investigate a missing person report that would unfold into a case that captivated the nation.

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 she stop because of recurring dizziness.

In the park, a panicked Rocha was rifling 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 were a series of lies Peterson told.

Peterson told Rocha he was fishing on San Francisco Bay, but later told Laci Peterson's uncle and two neighbors he had been golfing all day. He also was 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 very 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."

Prosecutors had more than a year to prepare what California Attorney General Bill Lockyer called a "slam dunk" case the day authorities arrested Peterson more than a year ago.

Defense attorney Mark Geragos (search) has countered that authorities unfairly targeted Peterson from the start, ignoring important leads that didn't fit their theory.

Geragos did not present his case Tuesday but made several objections during Distaso's presentation, including when the prosecutor said that a hair found on pliers in Peterson's small fishing boat irrefutably belonged to Laci. After speaking with Judge Alfred A. Delucchi in chambers, Distaso conceded in the afternoon that DNA results did not prove the hair was a definite match.

Prosecutors also were struggling with their own challenges: the absence of a murder weapon, a cause of death or an eyewitness to the crime.

They allege Peterson killed his wife on or around Dec. 24, 2002, in their Modesto home because he was having an affair, then concealed her body in his truck and drove nearly 100 miles to Berkeley and heaved it into the bay from the small boat he had purchased less than three weeks before. Investigators found a loaded .22-caliber handgun in the glove box of Peterson's truck, but have not said how they think he killed his wife.

The bodies of Laci Peterson and her fetus, a boy the couple planned to name Conner, washed ashore in April 2003, near where Peterson told authorities he set out on a solo fishing trip the morning his wife vanished.

Distaso stressed Peterson's affair with Frey, showing jurors slides in which he interchanged numerous pictures of the two, often embracing and smiling, with similar pictures of Laci and Scott Peterson.

Distaso said Peterson repeatedly denied the affair, even when a detective showed him the photograph of him and Frey that Frey faxed to police.

"He says, 'Is that supposed to be me?"' Distaso said.

Earlier in December, a friend of Frey's had confronted Peterson after hearing he was married.

"Scott Peterson ... he becomes very emotional," Distaso said. "He says, 'I lost my wife ... But I still tell some people that I'm married ... but I've lost my wife and this is going to be my first holiday season without her."

Prosecutors closed Tuesday's statements with multiple pictures of the severely decomposed bodies of Laci Peterson and her fetus. Several jurors winced and rubbed their heads, and Laci Peterson's relatives looked away.

Geragos has offered innocent explanations for the behavior of his client, who was carrying more than $10,000 cash and his brother's driver's license and had dyed his hair blond at the time of his arrest near the Mexican border.

He has floated a series of theories, including that members of a satanic cult abducted Laci Peterson and that the real killer framed Scott Peterson after learning his alibi, which was scrutinized in saturation media coverage.

It took nearly three months to find 12 jurors and six alternates in this county just south of San Francisco, where the trial was moved because a judge didn't think Peterson could get a fair hearing in the couple's hometown.