CAPE MAY COURT HOUSE — The discovery of a prosecution witness led Jason M. Thorn to plead guilty Wednesday to first-degree aggravated manslaughter Wednesday in the death of Wildwood resident Joshua Palumbo.

Jury selection for Thorn’s murder trial was expected to begin Monday, but Thorn opted to accept a plea agreement, rather than go to trial, in exchange for a 20-year prison term.

If convicted at trial, Thorn, 25, could have received a life sentence and not been eligible for parole for at least 30 years.

Defense attorney Scott Sherwood told Superior Court Judge Raymond Batten that the plea deal followed news that a previously missing witness who identified Thorn as the shooter had been located.

Details about the witness were not discussed during Wednesday’s proceedings. The discovery of the witness was enough for Thorn’s plea; he told the judge that a single gunshot wound to the chest killed Palumbo.

Thorn stood beside Sherwood, who asked him about Feb. 1, 2011, the day of the shooting.

Thorn, of Glenolden, Pa., admitted going to Palumbo’s apartment in the 100 block of Spicer Avenue about 10 p.m. that day.

He did not explain why he went there, but Chief Assistant Prosecutor Rob Johnson said “it was an arranged meeting,” adding the two men were not friends.

Thorn said he took a 9mm Luger with him and during the meeting pointed the handgun at Palumbo.

“Did you pull the trigger on the gun and shoot Mr. Palumbo?” Sherwood asked.

“Yes,” Thorn replied.

Thorn said he fired the gun just once, and the bullet hit Thorn in the chest. Palumbo was found dead inside his apartment between 10 and 11 a.m. the next day.

Thorn said he knew the gun was loaded when he went into the apartment, and he admitted it was reckless to carry a loaded firearm.

“And you ignored that risk,” Batten said.

“Yes,” Thorn said.

Thorn was arrested three days later at a home in Tinicum Township, Pa. He was armed with a handgun and taken into custody without incident, Cape May County Prosecutor Robert Taylor said at the time.

Johnson credited the Wildwood Police Department, the Prosecutor’s Office and Philadelphia authorities for working together to solve the case so quickly.

A Cape May County grand jury indicted Thorn in August, handing up a first-degree murder charge, and Thorn remained held in the Cape May County jail Wednesday afternoon in lieu of $1 million bail.

Sherwood said the plea agreement came about after he met with Johnson on Wednesday, the day several motions related to the case were to be heard.

Despite the plea deal, Sherwood told the judge that at sentencing he planned to argue for a shorter sentence than the 20-year term Johnson was requesting.

The 20-year prison term would be subject to the state’s No Early Release Act, meaning Thorn would have to serve at least 85 percent of the sentence before being eligible for parole.

Johnson told the judge he had consulted with Palumbo’s family, specifically his mother, about the plea arrangement.

Thorn is scheduled to be sentenced at 12:30 p.m. June 14.

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