Teen accused of killing friend for inheritance found guilty

Liam McAtasney was found guilty on all counts of murdering Sarah Stern, 19, a young artist who went missing from her New Jersey home in 2016.
2:54 | 02/27/19

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Transcript for Teen accused of killing friend for inheritance found guilty
Now a verdict in the case of a New Jersey man accused of killing his high school friend for her inheritance found guilty. Amy here with the latest. Good morning, Amy. Reporter: Good morning, George. This wassen eight-week trial with a chilling videotape but only took the jury less than a full day to deliberate. Guilty. Guilty. Guilty. Reporter: Overnight a former friend of 19-year-old Sarah stern found guilty on all counts of murdering the promising young artist who went missing from her New Jersey home in December 2016. A jury determining that Liam mcatasney strangled her and enlisted her prom date to help throw her body off a nearby bridge. To think that somebody that pretended to be her friend actually did that to her and -- without any remorse and -- it is painful. It's sad and it's just -- it's beyond anything that I've ever experienced before in my life and it's just horrible. Reporter: Prosecutors say the motive getting their hands on Sarah's lockbox which they believe was suffered with cash. The worst part of it I thought I was walking out 50 grand, 100 grand in my pocket. And she had one safe and she took money out and she only had 10 grand. Reporter: During the trial prosecutors playing what they say is a confession tape of mcatasney admitting to the killing. And it took me a half an hour to kill her. Reporter: Mcatasney did not take the stand in his defense. His attorney says his client fabricated that story for a horror film that a friend of his was working on. Prosecutors say when questioned by police just hours after stern's disappearance, that mcatasney intentionally misled investigators hoping to throw them off. Do you know why we're standing here talking to you? Do you have any idea where Sarah is? No idea. I just know she's been trying to get away. Reporter: Stern's grieving father telling reporters, justice was served. Sarah is up in heaven. She is an angel and she's -- she was just a beautiful person, she was a great kid and never should have ended like this. And our hearts go out to Michael stern. Liam mcatasney will be sentenced in may. He faces life in prison without the possibility of parole. I spoke with the prosecutor in this case and he says he is certain he will not see the light of day. That Liam mcatasney will spend the rest of his life behind bars. Boy, there is so much more of the story. You'll have two hours Friday. Yes, we are. It's a chilling story. It's just one of such unthinkable betrayal too. These were friends since first how could anyone do that but how could a friend do that? What the father is going through. It really is an unthinkable thing and said I don't want to add to your pain when we do these interviews. He said you couldn't possibly add to my pain and that was such a telling moment when I spoke with him. You're doing such great work on "20/20." Thank you. You really are. You can see it Friday night at 9:00.

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

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