Inmate charged in killing
County prosecutors say Lamar Gaines, 19, beat, choked, and suffocated Darryl Boone during an attack in October.
Boone, 38, was found by corrections officers who had entered the cell because they saw water flowing from under the door.
Gaines faces a life sentence if convicted.
The document says that Gaines admitted to using a torn sheet to strangle Boone and that he also sought to pour water on his unconscious victim in an attempt to drown him.
Authorities have not said what spurred the alleged attack, which occurred two days after authorities say Gaines attacked another inmate in the jail's gym. That attack left the inmate hospitalized and Gaines charged with attempted murder.
Gaines remains jailed on $2 million bail.
Gaines was being held in connection with a February 2012 robbery and carjacking.
Boone was being held on a recent vehicular-homicide charge.
He was charged in connection with the death a year ago of Jamere Cullers, 22, who was a passenger in a car driven by Boone that hit a pole in Trenton.