MICHIGAN CITY, Ind. -- Convicted murderer Gregory Scott Johnson says he doesn't deserve mercy, and that he has given up trying to save his life.

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Sister: He Just Wants Me To Live

But he says he wants to delay his execution to see if his liver can save his sister, and he rejects the arguments of those who oppose the request.

"The state of Indiana has waited to put me down for 20 years," Johnson (pictured, left) told ABC News in a jailhouse interview this week. "I don't know how bloodthirsty the citizens have to be through its elected government not to be able to wait for just a couple more weeks, or however long it takes, in order to save the life of someone who is innocent."

Johnson, who was convicted of killing his 82-year-old neighbor, Ruby Hutslar, in 1985, is scheduled to die by chemical injection on May 25.

Defense attorneys want the execution postponed for medical tests to see whether Johnson, 41, can donate part of his liver to his dying sister, Deborah Otis.

Death by chemical injection would ruin the organ. His attorneys say that if Johnson's liver is a match for Otis, part of his liver should be harvested, and then he can be put to death once he recovers.

In a jailhouse interview, Johnson said his request was a simple matter that should draw simple acceptance.

"I don't understand why they'd have a problem removing an organ if they don't have a problem with killing me in the first place, and the organ is going to someone who deserves to live," Johnson said.

Prosecutors call the last-minute request suspicious. Otis said her brother has only good intentions.

"I know this is going to be an ethical and political decision," Otis said. "It puts a lot of people under pressure. I understand that. That's not my intent or his. He just simply wants to help me live."

Johnson made his plea before a parole board on Monday. The board will hear more testimony Friday, and then it will make a recommendation to Gov. Mitch Daniels.

An aide to the parole board said the request is unlikely to sway the panel unless Johnson's attorney can prove a delay would be necessary to save Otis' life, RTV6's Norman Cox reported Tuesday.

The Indiana Supreme Court on Monday refused a request by Johnson's attorneys to reconsider the death sentence and whether an accomplice might have been responsible for the killing.