Transcript for New Jersey classmate murder verdict
verdict in a murder trial making national headlines. A young man in New Jersey convicted of killing a childhood friend. Prosecutors playing a secret recording at trial. My "20/20" co-anchor Amy robach following the case. Reporter: Late today, the young man accused of murdering his childhood friend in cold blood found guilty on all counts by a New Jersey jury. Prosecutors argued pure greed drove Liam mcatasney to strangle 19-year-old Sarah stern, a promising young artist who went missing from her home in 2016. She was a great kid and it never should've ended like this. Reporter: Jurors viewing this chilling tape police say was his confession. It took me a half an hour to kill her. Reporter: They say mcatasney planned to murder stern, then steal thousands of dollars her late mother left her. The worst part of it is, I thought it I was walking out 50 grand, 100 grand in my pocket. She had one safe that she took money out, and she only had ten grand. Reporter: Mcatasney claimed that video was merely an audition for a horror film. The jury didn't buy it. He will be sentenced in may. He faces life in prison without the possibility of parole. David? All right, Amy robach with us tonight. Amy, thank you. You can see much more of Amy's reporting on this chilling case, a two-hour edition of twbt twnt this Friday night, 9:00 P.M. Eastern. We'll see Amy on Friday night.
This transcript has been automatically generated and may not be 100% accurate.