Idaho prisoner allegedly killed his cellmate last year. He now faces a murder charge

BOISE (Idaho Statesman) — A 33-year-old prisoner at the Idaho prison complex south of Boise was indicted on a murder charge by an Ada County grand jury after he was accused of a fatal beating on his cellmate.

James M. Johnson, already serving time at the Idaho State Correctional Center on several prior felony convictions, was indicted last week with a first-degree murder charge in the death of fellow prisoner Milo Warnock, the Ada County Prosecuting Attorney’s Office announced Tuesday.

Grand jury indictments are sealed until the suspect is served with a warrant and makes their first court appearance.

Warnock, 45, died less than an hour after an in-custody assault in December, the Idaho Department of Correction previously announced. Warnock’s family is pursuing a lawsuit related to his death from multiple blunt-force injuries and has awaited charges against the alleged perpetrator for nearly nine months.

The Idaho State Police investigated the attack on Warnock. After Warnock’s death, Johnson was transferred to the complex’s maximum security prison, where he remains today, according to prison system records. His prison sentence for his prior convictions, which included possession of a controlled substance, grand theft and fraud out of Bannock County, were set to be satisfied in February 2025.

Warnock was serving up to 10 years in prison following his second DUI conviction since 2013, according to prior Idaho Statesman reporting. He could have been released after two years in prison but was moved to a more secure area of the prison after breaking rules related to receiving his prescribed medication, his mother, Kathy Warnock, previously told the Statesman.

Before his death, Milo Warnock told his family he was having trouble with his new cellmate, having stated that the man was “mentally disturbed” with “a pattern of escalating behavior,” the Statesman previously reported. The Warnock family is seeking almost $500,000 from the prison system, several of its employees and the prison’s health care contractor.

If convicted of Warnock’s murder, Johnson could be sentenced to the death penalty or life in prison. He faces no less than a decade in prison. Johnson’s next appearance in court is scheduled for Sept. 18, according to the Prosecutor’s Office.