The 34-year-old Matias was indicted Tuesday on a murder charge. He is being held at Bellevue Hospital.
Authorities say he told police he throttled his daughter, Ana, with an electrical cord after finding her sending risque messages to a boy.
Matias pleaded not guilty last month to murder and manslaughter during a bedside arraignment at the hospital.
Matias was charged with the murder of his daughter, Ana Matias. The cause of her death was homicidal asphyxia, the medical examiner said.
During the bedside arraignment, Bronx Assistant District Attorney Elizabeth McGrath read from a rambling statement Matias gave to police and prosecutors.
It said Matias initially picked up a bat, but, fearing blood, instead tied a knot around an electrical cord and used it to strangle his daughter.
"I want to serve 30 to 50 years," Matias said, according to the statement. "I strangled her. I choked her. I killed her."
He said he killed the daughter because he found her writing "sex things" to a boy.
Matias had called 911, claiming he had strangled his daughter Friday night and had dumped her body in a wooded area in the Bronx.
But when officers searched his apartment building, where he served as superintendent, they discovered the partially burned body in the boiler.
Ana Matias had been visiting her father, but lived in Pennsylvania with her mother and two sisters. Police say the parents were separated and Matias had visitation rights, even though he had a history of emotional problems and was institutionalized after trying to set a car on fire with the children inside in Pennsylvania.
It wasn't clear how long ago that incident occurred, or the length of time he was institutionalized. The daughter, believed to be in the car when Matias tried to burn it, was the only child visiting him at the apartment.
