Andrew Conley, 18, entered his plea as jury selection was to begin for his trial in the small Ohio River town of Rising Sun, Ohio Circuit Court administrator Connie Sandbrink said.

Sandbrink said Conley didn't have a plea agreement with prosecutors, who intend to seek the maximum sentence of life in prison without parole. His sentencing hearing was scheduled to begin Wednesday, and Sandbrink said it was expected to last three to four days.

Conley was to be tried as an adult but couldn't face the death penalty because he was 17 when his brother, Conner, was killed last November. Defense attorneys had been expected to argue Conley was insane at the time. Negangard had described the teen as "just evil."

Police say Conley told investigators he had fantasized about killing people since he was in eighth grade, and that on the morning of Conner's death, he stood over his sleeping father with a knife and thought about killing him. He also said he identified with the fictional television serial killer Dexter.

The teen told investigators he wrestled his brother unconscious, strangled him and then put his body in a trunk, where it stayed while Conley stopped to give his girlfriend a "sweetheart ring," according to a police affidavit. He later dumped the boy's body in a park near a school, the affidavit said.

Conley said he strangled Conner because, "I felt like I had to" and likened the urge to a hungry person satisfying a craving for a hamburger, according to the document.

Psychiatrists who have not examined Conley but who have studied similar violence by teens said the behavior some characterize as evil can defy explanation.

Friends and neighbors have described the Conley family as "strong" and "balanced" and said both boys were good students who stayed out of trouble.