Young man on trial for the murder of his childhood best friend

A secret recording is now at the center of a murder trial, as a young man is on trial for killing his childhood friend.

Sarah Stern, 19, went missing from her New Jersey home in Dec. 2016.

Her childhood friend, Liam McAtasney, is charged with strangling her.

The motive? According to prosecutors, getting his hands on Sarah's lock-box he believed was stuffed with cash.

Prosecutors played the secret confession tape Thursday in court.

McAtasney can be seen in a car, talking about how he thought Sarah's lock-box was going to be stuffed with $50,000 to $100,000 in cash, but instead he only found $10,000.

They also showed body cam footage from just hours after Stern was reported missing.

When the police approached McAtasney and asked him if he knew where Stern was, he attempted to throw them off by telling them that she had been trying to get away and had plans to move to Canada.