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A convicted murderer said in a letter written from death row that the South Dakota Supreme Court owes it not only to him but to the family of the prison guard he killed to allow his execution to take place in a timely manner. It's the only way, he said, the guard's family can get justice.

Eric Robert, 50, pleaded guilty to killing Ron Johnson during a botched prison escape at the South Dakota State Penitentiary and asked to be put to death. A judge determined in October that the crime merited the death sentence, and Robert was scheduled for execution the week of May 13.

But the state Supreme Court postponed the date in February to allow more time for a mandatory review to make sure the death penalty was proper, even though Robert hadn't appealed the conviction or sentence. The review could take up to two years.

In a three-page letter to The Associated Press, Robert detailed why he believes the death sentence is appropriate in his case and described his aggravation with the delay. The letter represented Robert's first public comments since his October sentencing.

He said justice works differently in death penalty cases than in others.

"Victims of non-capital offenses receive their justice when the perpetrator is placed in custody. Victims in capital cases receive their justice when the perpetrator is executed. Give the Ron Johnson family their justice, they have been forced to wait too long. I finish where I started — I deserve to die," he said, alluding to a statement he read during his trial that started with "I deserve to die."

Robert, a chemist who worked for the Environmental Protection Agency before overseeing a city water treatment department, was serving an 80-year-sentence on a kidnapping conviction when he attempted to escape April 12, 2011, with inmate Rodney Berget.

Robert contends he was drunk and trying to rob an 18-year-old woman of $200, not sexually assault her, in the kidnapping case. He was sentenced to 80 years in prison and would not have been eligible for parole until he was 83. He focused obsessively on getting his sentence reduced, but his appeal was denied in 2009, leading to what the judge at his death penalty trial called an "internal war" that eventually left Johnson dead.

Johnson was working alone on the morning of his death — also his 63rd birthday — in a part of the prison known as Pheasantland Industries, where inmates work on upholstery, signs, custom furniture and other projects. Prosecutors said after the inmates killed Johnson, Robert put on the guard's uniform and tried to push a large box on a cart containing Berget to the prison gate. The inmates were apprehended before leaving the grounds.

In his letter, Robert noted that everyone agrees he is mentally competent.

"Yet, as recently as May 8, 2012, the (South Dakota Supreme Court) was still nosing around this issue. They just can't seem to fathom that a defendant would accept a just fate," he wrote, later adding he has a right to plead guilty and receive the death penalty. "I am free to admit my guilt, as well as acknowledge and accept society's punishment just as I am free to proclaim innocence in defiance of a verdict. I believe that the sentence of death is justly deserved in any murder and should be carried out."

Robert said the issue at hand is not about him wanting to die. Instead, it's about the Legislature providing the South Dakota Supreme Court with adequate guidance on how to handle a sentence review when there's no appeal.

In court briefs recently filed by his lawyer, Robert proposed the Legislature consider changes to the law, allowing death penalty proceedings to be given priority in the state Supreme Court or, absent an appeal, requiring the court to review the case in a set number of days before the execution date.

The briefs noted the state Supreme Court has reviewed numerous cases, including a civil dispute between actor Kevin Costner and an artist about whether sculptures were appropriately displayed at a Deadwood resort, while Robert's case is still pending.

The justices noted in their February decision that unless a proper review is done before Robert is killed, the execution could be found unconstitutional under death penalty guidelines established by the U.S. Supreme Court.

The other inmate who tried to escape, Berget, 50, also pleaded guilty and was sentenced to death, although he is now appealing both his conviction and sentence. A third inmate, Michael Nordman, 47, was given a life sentence for providing the plastic wrap and pipe used in the slaying.

The penitentiary boosted security after Johnson's death, including adding officers, installing more security cameras and mandating body alarm "panic buttons" for staff.

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