An American teenager who admitted he strangled his 10-year-old brother and told police he identified with a TV serial killer was sentenced yesterday to life in prison without parole.

Andrew Conley, 18, showed no emotion as a judge sentenced him for the 28 November 2009 murder of his brother, Conner. But the teenager wept as he was led out of the courtroom.

Judge James Humphrey could have sentenced Conley to life in prison without parole or to a lesser term of 45 to 65 years. But Humphrey said Conner's age outweighed any other factors such as mental illness.

"He deserved life, and that's what he got," said Dearborn-Ohio County Prosecutor Aaron Negangard. Defence attorney John Watson said Conley would appeal the sentence.

"He was a 17-year-old boy and there was evidence of mental illness," he said.

In a chilling video played during a five-day sentencing hearing last month, Conley calmly described how he killed Conner while wrestling with the boy at their home in southern Indiana.

The teenager told police he caught his brother in a choke hold as the child fought and pleaded for him to stop. Instead, Conley said he choked Conner until he passed out, then dragged the boy into the kitchen, put on gloves and continued strangling him for at least 20 minutes. He then loaded his brother's body into the trunk of his car and drove to visit his girlfriend before dumping his body under some leaves along a park trail.

Conley told psychologists he had been unable to stop and felt as if he were watching the murder from outside himself. He also claimed he heard voices. Three experts who examined Conley said he was severely mentally ill, while a fourth who didn't interview him said he believed Conley showed signs of being a psychopath.