Case Facts: 

On November 24, 1985, Mark Steffenhagen and Parkus were inmates in the Missouri State Penitentiary (MSP), in housing Unit 2-B, a Special Treatment (protective custody) Unit for prisoners who had been threatened with sexual abuse or had exhibited suicidal tendencies.

Steffenhagen returned from supper sometime between 5:30 and 6:00p.m. and was found strangled in his cell about 7:15.

Larry Weixelbaum, an inmate walkman on fourwalk, who described the routine followed by inmates returning to their cells from supper, stated that upon leaving the dining hall, they returned to their walks and waited at their cells until the guard simultaneously opened all doors, at which time each entered his cell and the doors were locked.

On the evening of the murder, Weixelbaum was released from his cell after lockdown to perform his duties as walkman and as he moved along the corridor he noticed the bars of Steffanhagen’s cell, number 116, were covered by a blanket but he thought little of it because Steffanhagen often put up a blanket for warmth.

At about 7:15, Weixelbaum heard someone calling from Steffanhagan’s cell and he saw a hand "waving him over". He went to the cell and Parkus, who was there instead of his own cell, shoved the blanket aside and said "man you got to get me out of here".

The light in the cell was then turned on and Steffenhagan was lying on his left side on the bed. Weixelbaum told Parkus to roll him over to see what was wrong. Parkus said "man he ain’t breathing, I think I killed him. You are going to have to get me out of here". Weixelbaum notified Sergeant Richard Hagendorf.

As Hagendorf made his way to fourwalk he released the lock on cell number 116. As Hagendorf approached the cell, Parkus stepped in the hall and said "he didn’t do nothing" and tried to walk away.

Parkus was ordered to stay in front of the cell while they examined Steffanhagan. Parkus began to run for the stairs but was caught by Hagendorf and was placed in handcuffs and moved to a secure area.

The autopsy of Steffenhagan revealed scrapes on his nose and chin and a cut on the lip suggesting he had been struck by a blunt object such as a fist. Bruises on the back of his hands, wrist and ankles indicated his arms and legs had been tied and that he had struggled. External contusions to the neck as well as internal damage to the larynx demonstrated the cause of death was manual strangulation.

In this undated photo provided by the Missouri Department of Corrections, Missouri inmate Steven Parkus is shown.

The Missouri Supreme Court spared Parkus, 46, a convicted murderer from execution Tuesday, April 17, 2007, by upholding a lower court decision that he is mentally retarded. As a result of the unanimous ruling Parkus will instead serve a life prison sentence.