The trial of Jeremy Brent Cramer of Lacey, Wash., is scheduled to start on April 7, The Montana Standard reported Saturday.
He could face up to life in prison if convicted of mitigated deliberate homicide in the death of his son, Broderick.
Cramer has pleaded not guilty to beating and stabbing his son and remains jailed on $250,000 bond. Prosecutors say he might have been under the influence of a prescription stimulant.
The decision by Anaconda-Deer Lodge County prosecutors against seeking the death penalty was filed on Aug. 16.
Employees at an Anaconda convenience store called police on July 8 to report seeing Cramer trying to wash blood from his clothing in the restroom.
Cramer phoned his father after he was arrested and told him in the recorded call that he had run out of gas and started walking down the rural road with his son on his shoulders, according to prosecutors.
Authorities say the boy's body was found the next morning near Cramer's abandoned truck about 5 miles southeast of Anaconda.
A partial transcript of the phone call says Cramer told his father he killed his own son, and he didn't know why. He asked "'Why did I take all my pills?'" according to the transcript.