BALTIMORE (Map, News) - The 23-year-old man charged with strangling a fellow inmate aboard a state prison bus should not be held criminally responsible because he didn’t get enough treatment in prison for mental illnesses that led to the attack, defense attorneys said Monday.

Kevin G. Johns, 24, suffered depression and psychosis and heard voices since age 8, defense attorney Harry J. Trainor said in opening arguments in Harford County Circuit Court.

But Assistant Baltimore County State’s Attorney S. Ann Brobst said Johns strangled 20-year-old Philip Parker Jr. aboard the bus, bound for Baltimore, after Parker testified in his favor at a sentencing hearing the previous day.

“[Johns] felt angry at the sentence he received,” Brobst said. “This was an act of retaliation.”

 She also said Johns confessed that killing causes him to become sexually aroused.

Trainor said Johns lived most of his life in institutions. He was removed from his Baltimore home by Social Services at age 6, then moved from hospital to hospital for mental ailments including post-traumatic stress disorder, hallucinations, suicidal tendencies and attention-deficit hyperactivity disorder. He was treated until he turned 18, Trainor said.

“Kevin was released on his own, completely unprepared for life outside an institution,” Trainor said. “By 2002, he began his life as a convict.”

Johns was convicted in 2002 of killing his uncle, saying Satan told him to do it. While serving a 30-year sentence in Hagerstown for that offense, he was convicted of killing his 16-year-old cellmate and sentenced to life without parole.

Trainor said Johns was not getting enough treatment in prison to control his mental illnesses and dangerous impulses.

“Without treatment, he lacks the ability to control his behavior, and on Feb. 2, a life was lost because of that,” he said.

Circuit Judge Emery Plitt will hear the case, after Johns waived his right to a jury trial. He will get to choose again between a judge and a jury if he is convicted and faces the death penalty, Plitt said.

Five men from the Division of Corrections escorted Johns into the courtroom and remained beside him. Plitt said that Johns was being left in handcuffs, a chain around his waist and leg irons to prevent his escape, to prevent him from harming others and to keep order in the court.

“I don’t understand why,” Johns said, but after that his only other replies to Plitt were “yes” or “no.”

Brobst said the case could last three to four weeks.

msantoni@baltimoreexaminer.com