I-TEAM: Scott Peterson's secretly recorded conversations reveal lies, evidence

MODESTO, Calif. (KGO) -- The ABC7 News I-Team obtained access to more than a thousand pieces of evidence, including photos, documents, and recordings -- some of it has never made it to the public.

When Laci Peterson vanished on Christmas Eve 2002, her case captured the national spotlight and it still does.

Scott Peterson was convicted of murdering his pregnant wife and their unborn son Conner.

TIMELINE: How the Laci Peterson case unfolded

Laci Peterson, who was 8 months pregnant, went missing from her Modesto home in 2002.

Just hours after Laci's family reported her missing, Scott did his first and only in-depth interview with police. "She told me what she was going to do for the day," he said. "She was going to finish cleaning up, take the dog for a walk."

Detective Allen Brocchini asked Peterson about going fishing on Christmas Eve. "When did you realize you were going to go fishing?"

"Was a morning decision to go golf at the club or go fishing -- seemed too cold to play golf at the club," Peterson answered.

"Okay... it's Christmas Eve. you're gonna go fishing because it's too cold to go golfing -- that's crazy," Brocchini told ABC's 20/20.

When Brocchini asked Scott if he had a map for the area, he responded, "no."

Brocchini and his partner Detective Jon Buehler were on the case from day one.

EXCLUSIVE: Laci Peterson's mom talks moment she doubted son-in-law Scott

The murder of Laci Peterson and her unborn son Conner still draws worldwide attention almost 15 years later. The I-Team has an exclusive interview with her mother and what she says happened the last time she saw her daughter alive that made her doubt her son-in-law, Scott Peterson.

"The first person you focus on in a homicide investigation is the person closest to the victim and the last person to see the victim. And of course, boom, boom--we got both of those with Scott," said Buehler.

Police photos show how every dimension of Peterson's boat and truck were measured. An evidence tech similar in height and weight to Laci was used to examine how the boat and truck may have been used.

"There's places you could drive 15 miles. But you're gonna drive 90 miles to the San Francisco Bay. I know you don't go out in the Bay in a 14-foot boat," Brocchini added.

In court, prosecutors showed the jury parts of a videotaped interrogation to highlight Peterson's demeanor.

"What concerns me the most is doing anything I can to further the progress," Peterson said.

RELATED: Scott Peterson speaks from death row on Laci Peterson murder

New Year's Eve marked five days after Laci disappeared, with search efforts underway. Police heard Scott lying to an unidentified woman on a secretly recorded phone call.

Peterson, a fertilizer salesman has told her he was traveling overseas on business. "I'm near the Eiffel Tower and the New Year's celebration is unreal. The crowd is huge," he said on the call.

Investigators recorded more than a dozen telephone conversations between Peterson and his mistress, 30-year-old Amber Frey, a massage therapist and single mother.

She met Scott in Nov. on a blind date. Five weeks later, Laci went missing.

Frey says Scott never told her he was married or about to become a father. But when Tabloids broke the story of their relationship, Peterson called Amber to admit he'd been lying.

"I don't want to do this over the phone," he said on another secretly recorded call. "I have not been traveling during the last couple of weeks -- I've lied to you. The girl I'm married to, her name is Laci. She disappeared just before Christmas. For the past two weeks, I've been in Modesto with her family and mine -- searching for her."

He continued, "I've been hunted by the media. I'm destroyed and God -- I hope so much that this doesn't hurt you."

"Scott, are you listening," Frey responded. "You came to me early in December and told me that you lost your wife. What was that about?"

Scott : "She's alive."

Amber : "What?"

Scott: "She's alive?"

Amber: "Where?"

Scott: "In Modesto -- sweetie I can't explain anymore now."

Frey was a key witness against Peterson both on these tapes and at his murder trial.

Amber: "This fear inside my heart that you had something to do with this and you may have possibly and potentially have killed your wife..."

Scott: "No, you don't need to have that fear. You know me well enough. I'm not an evil guy."

Click here for more information on the Laci Peterson murder case.