The 19-year-old man accused of murder, conspiracy and other charges in the death of a young New Jersey woman told a friend he choked her and then watched for half an hour as she died in her home, prosecutors said at a court hearing Tuesday.

Liam McAtasney, of Neptune City, was ordered to remain behind bars as he awaits trial in the slaying of his childhood friend Sarah Stern, who was considered a missing person for months after she vanished from her home in early December.

Prosecutors say McAtasney robbed and strangled Stern, 19, at her home Dec. 2, then dumped her body off the Route 35 Bridge in Belmar with the help of an alleged accomplice who once had taken the victim to prom. 

At Tuesday's court hearing, prosecutors revealed McAtasney allegedly admitted the crime to a friend, and the friend, unbeknownst to the alleged killer, had videotaped the conversation. On the recording, McAtasney is allegedly heard saying he strangled Stern with such force her body was lifted off the ground -- and then he timed how long it took her to die, prosecutors said.

Charles Moriarty, McAtasney's attorney, didn't fight the judge's decision to remand his client, but said after court the young man was innocent, according to NJ.com. 

McAtasney and his suspected accomplice, 19-year-old Preston Taylor, were arrested in the case earlier this month. The two allegedly dumped Stern's body off the bridge after hiding it in the bushes behind her home for eight hours. 

Prosecutors have said McAtasney was motivated by robbery in part and stole thousands of dollars from Stern. Cash was found in a safe buried at a park in Neptune. Stern's clothing was found in another safe buried on Sandy Hook. 

At a court hearing last week, prosecutors said Taylor, who took Stern to junior prom, told police McAtasney had planned Stern's slaying for six months. 

Meanwhile, the search for Stern's body continues. Divers and helicopter units first scoured the Shark River in early December after finding Stern's fully operational car parked on the shoulder of the southbound lanes of the bridge, the keys still in the ignition, Dec. 3. 

Investigators returned there several weeks ago to continue looking, acknowledging that currents and tides may have swept her body out to the Atlantic. Monmouth Prosecutor Chris Gramiccioni said at the time, "We are hoping for a miracle." Stern's family has said they just want to bring her home.

Stern, an aspiring artist, is a graduate of Neptune High School, where she played softball and was a member of the swim team. She went to Brookdale Community College for a year, where she studied art and TV production.