Conley told police he held his brother in a choke hold while wrestling at their rural home and dragged him into the kitchen after he passed out, where he strangled him for 20 minutes. He then wrapped the boy's head in two plastic bags.

A coroner testified that Conner may have still been alive for minutes or hours after that point, but the bags helped suffocate him, and Conley repeatedly banged the boy's head on the ground before loading him in the trunk of his car to make sure he was dead. He then drove to his girlfriend's home and gave her a promise ring, while Conner's body was still in the trunk of his car.

The two justices who dissented in Tuesday's ruling, Robert Rucker and Frank Sullivan, cited the teen's age when arguing that he shouldn't have been sentenced to die in prison.

"There is no question that juveniles have developmental issues that reduce their culpability for crimes," Rucker wrote.

Dearborn-Ohio County Prosecutor Aaron Negangard, who handled the case, said the high court made the right decision.

"It is the just result given the nature of the crime that he committed," Negangard said.