Transcript for Laci's Peterson's body discovered, Scott Peterson goes to trial: Part 2
Now back to the disappearance of Laci Peterson -- Reporter: Early 2003. Laci Peterson, then 7 1/2 months pregnant, is missing. And all eyes are on her husband, Scott Peterson. How are you doing personally, how are you holding up to all of this? Tremendous strain, obviously. Got anything to say? Is there anything you want to say? It was crazy. It blew out of control. It was a tsunami. A frenzy. He was the most hated man in America at that time. This morning an exclusive interview with Scott Peterson. Reporter: In his first network television interview, Scott sat down with ABC's Diane sawyer. I think everybody sitting at home wants the answer to the same question. Did you murder your wife? No. No. Eat just -- I had absolutely nothing to do with her disappearance. And I know that suspicion has turned to me. Because of the inappropriate romantic that I had with amber Frey. Did your wife find out about it? I told my wife. When? Early December. A lot of arguing? No. There wasn't a lot of anger? No. Do you really expect people to believe that an 8 1/2 month pregnant woman learns her husband is having an affair and is saintly and casual about it? Accommodating? Makes a peace with it? Well, I -- yeah. I -- you don't know -- no one knows our relationship but us. Reporter: Less than three months later, on the shores of San Francisco bay, a breakthrough in the case. The contra Costa county coroner has arrived on the scene and has recovered the remains of the victim. When the bodies came up, it automatically injected a big sense of urgency in the case. I just thought, we got to find Scott. We knew he was in saying at the time. Didn't have a tracker on his car. San Diego was pretty close to the Mexican border. When Scott was by the exit to Torrey pines and they turned on the red and blue lights and stopped him at the entrance -- This is a tragedy. It is affecting many lives. Scott Peterson has been arrested. There are no other suspects in this case. I went out once the vehicle was there to do the inventory search on it. And just a whole bunch of stuff in the car. Guy had $14,000, $15,000 cash, his brother's I.D. Camping supplies. Some ropes, knifes. 15 pairs of shoes and hiking boots. Shovel, fishing poles. He had dyed his hair red, he had a goatee. Like James bond on a secret agent mission. Clearly he was getting ready to possibly go somewhere and hide out. Reporter: Modesto police took Peterson into custody. He was charged with capital murder. Suddenly a sleepy, sluggish little town like Modesto is transformed into a media circus. Reporter: No cameras were allowed inside the courtroom. At trial the defense would argue that Laci was abducted but by someone else. The most likely thing that happened is that she was abducted and she was abducted by someone other than my client. And that she was abducted while walking her dog. On the 24th, the neighbors across the street left their home to go to Los Angeles. Someone robbed their home. This is right across the street from the Peterson house. So when this information came out, immediately there was a sense that, okay, maybe Laci, who was walking the dog, came across this burglary and that's what happened to her, maybe she was taken away. Reporter: The prosecution, meanwhile, arguing that Scott was responsible for murdering his wife and unborn child. I thought, basically innocent. For a long time. Then it started going -- shifting the other by. There was a lot of evidence against Scott Peterson, all right? It was a circumstantial evidence case. But that doesn't mean it was weak. It was a very strong, powerful, compelling case. They looked at his computer use. And they saw that he was looking at the currents in the San Francisco bay. There was two separate really strong pieces of evidence that worked together. The fact that the bodies were in the bay where Scott put himself. And the other significant aspect about that is, Scott predicted that this was going to happen to Laci weeks before it happened. When he met with amber Frey at the beginning of December. This has to be the biggest coincidence I have ever heard of. I mean, are you psychic? You predicted your wife would be missing? On August 10th, when amber Frey started her testimony and those recordings started to play, there was a turning point for the prosecution. From the moment I learned the truth, it wasn't about me. It was about a missing pregnant woman. There was information that I had that nobody knew or heard. Amber Frey and those tapes totally turned the case upside down. And it sunk Scott Peterson. Scott realized that as soon as it came out that it was amber, all bets were off. Oh, yes, you said you lost your wife. No, that -- yes -- Obviously without me saying much. I said that I lost my wife. Yes, you did. I did. And yes -- How did you lose her then, before she was lost? Explain that. There's different kinds of lost, amber. A guy supposedly out there searching desperately to find his missing wife. And he's telling this girlfriend he lost his wife? That's a tough piece of testimony to overcome. Reporter: Then on November definite butterflies when we got word that there was a verdict. We, the jury, in the above-titled cause find the defendant, Scott Lee Peterson, guilty of the crime of murder -- There was gasps from the defense side. Just like, oh! They couldn't believe it. They absolutely could not believe it. You could see it. They just -- they were stunned. Reporter: A guilty verdict. And at sentencing, Scott Peterson is given the death penalty. What convinced you to choose the sentence of death? I played in my mind over and over, conspiracy, was somebody trying to set up Scott, was somebody after Laci? It didn't add up, for me. What a nightmare. It hasn't changed. It's still a nightmare. It should never have happened. It's hurt too many people for no reason. But justice was served. Obviously we're very disappointed. Obviously we plan on pursuing every and all appeals. Guess what, Scotty? San Quentin's your new home. And it's illegal to kill your wife and child in California.
This transcript has been automatically generated and may not be 100% accurate.