Courtesy KELO-TV, File, Associated Press
FILE - This July 18, 2012, file frame grab provided by KELO-TV shows convicted killer Donald Moeller during a court appearance in Sioux Falls, S.D. A public defender on Thursday, Oct. 4, 2012, asked a judge to appoint a guardian for the convicted killer saying he's incompetent and incapable of making voluntary and rational decisions in a federal suit challenging South Dakota's capital punishment procedure. Moeller is to be executed in October for the 1990 killing of 9-year-old Beck O'Connell.

SIOUX FALLS, S.D. — Donald Moeller regularly reads the Bible while on death row, but the graying 60-year-old is forgoing mercy and taking an Old Testament approach to his fate.

For the first time, Moeller admitted Thursday that he kidnapped, raped and killed 9-year-old Becky O'Connell more than 20 years ago. He told a federal judge that what he did was evil and that he has to pay for it.

"The law has spoken," said Moeller, who was twice convicted of first-degree murder in the 1990 slaying. "I killed. I deserve to be killed."

U.S. District Court Judge Lawrence Piersol ordered Moeller to appear at Thursday's hearing, which was supposed to deal with the constitutionality of South Dakota's one-drug capital punishment procedure. But the proceedings have become mired in a series of bizarre motions that pit Moeller's state-court lawyer against Arkansas-based public defenders arguing the federal case.

Piersol listened to arguments about the attempt to dismiss but not specifics on the lethal injection protocol. He took the dismissal under advisement and will rule later. Moeller is scheduled to be executed in late October or early November.

The Arkansas lawyers contend that the execution method using pentobarbital violates the constitutional ban on cruel and unusual punishment, but there are few details about those issues as many of the recent filings have been kept under seal.

Piersol told Moeller that the attorneys allege there's a high probability that solely using pentobarbital in the execution could cause him pain, and asked if Moeller still wanted to dismiss the appeal.

"Yes, I do," he responded.

Authorities say Moeller kidnapped O'Connell from a Sioux Falls convenience store, drove her to a secluded area near the Big Sioux River, and then raped and killed her. Her naked body was found the next day; she had been stabbed and her throat was slashed.

Just before the hearing Thursday, Little Rock, Ark.-based attorney Scott Braden filed a motion asking Piersol to appoint a guardian for Moeller, saying he's incompetent and incapable of making voluntary and rational decisions. An affidavit from a psychology professor said Moeller's abusive upbringing and time in solitary confinement have undermined his will to live.

Moeller disputed the assessment of his mental state.

"Judge, I know what's happening. I am competent, and I don't want this dragging through the courts anymore," he said.

Braden said Moeller has not been informed properly about South Dakota's execution protocol, mistakenly telling the attorney he thought the state was going to use propofol, the "drug that killed Michael Jackson."

Moeller said he might have misspoken but knows what lies ahead.

"They're going to put poison in my veins and they're going to kill me," he said.

"I've OD'd before. I'm not scared."

Attorney Mark Marshall, who was appointed to represent Moeller in his state court case, said Moeller has wanted to drop the federal challenge for months and the Arkansas attorneys have refused.

Marshall told the judge that Moeller has dismissed the case and no ruling is required, but Piersol told him that he can ask questions before deciding whether to accept that dismissal.

Moeller initially was convicted in 1992, but the state Supreme Court overturned it, ruling that improper evidence was used at trial. He was again convicted and sentenced to die in 1997.

Piersol has upheld the constitutionality of Moeller's conviction and sentence, but hasn't ruled on South Dakota's execution protocol. Piersol told the attorneys Thursday that the case is not about whether Moeller will be executed, but how — and possibly when — the punishment will be carried out.

Moeller said he doesn't have a death wish, but executing him is "right." He said if the rape and killing of a little girl doesn't warrant the punishment of death, then nothing does.

"I don't want to be executed," Moeller said. "I don't want to die. I want to pay for what I owe."