WATCH: Liam McAtasney, Sarah Stern's childhood friend, goes to trial for her murder: Part 9

WATCH: Liam McAtasney, Sarah Stern's childhood friend, goes to trial for her murder: Part 9

Transcript for Liam McAtasney, Sarah Stern’s childhood friend, goes to trial for her murder: Part 9

Ladies and gentlemen, Sarah stern will not be walking through those doors at any point. Her friends and family will never get to enjoy her company, her smile, her laugh. It’s not because she disappeared to Canada. It’s because this defendant murdered her. You are going to hear that Sarah stern wanted to leave new Jersey. She wanted to get away. Not only from her dad, but the entire city. The prosecution comes out swinging. Their first witness with Preston Taylor. Do you guys ever talk about specific plans with this money? Yes. He ultimately admitted to a large role in all this. It started as plans to figure out how to rob her personally. Over time the conversations progressed to killing her in order to obtain the money. You were part of these conversations, correct? Yes. Specifically, it was decided that Liam would strangle her. And is that the person that you and Mr. Mcatasney threw off the bridge that night? It is. The key for prosecutors here was ruling out the two other possibilities, that she fled to Canada or that she committed suicide. They called witnesses to try to prove she wasn’t suicidal and she wasn’t going to Canada. I told her she couldn’t run off without a plan. She needed to save some money. Did you have any reason to believe that she was sad or depressed? Absolutely not. There was a real heartfelt moment at court when the bank manager took the stand and talked about his last exchange with Sarah stern on the day she went missing and it was an emotional moment that everyone in the courtroom felt. Do you remember seeing Sarah on that day? I do. I blew her a kiss, waved goodbye. And what did you say to her? I said “I love you,” because she — we had that friendship. Testimony resumed this morning in the Sarah stern murder trial. Stern’s father testified about her sudden disappearance. Her remains have never been found. At some point on December 2nd, do you receive a phone call from somebody in New Jersey? Yeah. I got a call from my mother, who said she hadn’t been able to get in touch with Sarah for the whole day. So what do you do? I sent her a text. Sent another text, “Hello?” I sent another text, it says, “Sarah, what’s going on?” What was it like being up on the stand? It was a little nerve wracking, but I had to be there. You took the stand at trial. And you could look right at Liam from where you were testifying. Did you look him in the eye? I tried. He wouldn’t look at me. I looked at him and he just stared away. Sociopath? Obviously. Evil? Definitely. Part of the evidence that was presented at trial were text messages Michael stern was sharing when he first realized his daughter went missing and you could see the panic he was experiencing during those moments. And then I sent another one right after that that says, “Call me as soon as you get this message”, in caps. Are you starting to get nervous? Yes. All right. On December 3rd at 12:30, do you text her again? Yes, I sent another message that said, “Call me”, with a couple exclamation points. Did she answer? No. When you interview people, one of the important things to understand is, do they have agendas in telling you a particular bent to a story? I’ve been friends with her since first grade. So we have a pretty good He wanted to picture Sarah as having this abusive, relationship with her father. I know she definitely has a lot of trust issues with her dad. And then if you look at the text messages the police found, her relationship with her father was nothing like Liam had painted it. “Hey, dad, good afternoon. What day are you coming back from Florida?” Then there’s a waving hand, sun glasses on a smiley face, a palm tree, and a little red car. I sent her a picture of a rainbow that had just appeared right around that time. Do you send her a second picture? It’s a picture of the castle in the magic kingdom at night. What does she say? “Wow!” With an exclamation point. “The castle looks so pretty with the lights.” And there’s a star and a shooting star emoji after that. Okay. Is that the last time you’ve ever had contact with your Yes. I think being able to present their relationship was also very, very important because it takes away from that notion that this little girl would disappear because her father was so horrific she had no other choice. The defense’s strongest argument is that some of the details don’t match with some of the evidence. There was no blood recovered from the interior of that house, correct? No, sir. There was no urine recovered from the interior of the house? No. It’s a very typical defense argument, which is not everything fits. The problem for the defense is, that if you look at it in its whole together, it all does kind of fit. The biggest hurdle for the prosecution to overcome? There’s no body. In the 11th hour the defense calls an eye witness — There was a picture of a girl. I said to my son that’s who we His testimony could turn this

This transcript has been automatically generated and may not be 100% accurate.

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