John David Duty Execution: Animal Sedative Used in Okla. Inmate's Execution

MCALESTER, Okla. (CBS/AP) Convicted murderer John David Duty was executed Thursday evening in Oklahoma, using a drug combination that included pentobarbital, a sedative often used to euthanize animals.

He was pronounced dead at 6:18 p.m. at the Oklahoma State Penitentiary.

The 58-year-old, who was sentenced to die for strangling his cellmate in 2001, is believed to be the first person in the United States whose execution included the use of pentobarbital. A nationwide shortage of a key ingredient had forced the state to tinker with the usual formula used in executions.

Strapped to a gurney, with an eye patch covering his right eye, the heavyset Duty apologized to the family of his victim, 22-year-old Curtis Wise.

"I hope one day you'll be able to forgive me, not for my sake, but for your own," Duty said. "Thank you, Lord Jesus. I'm ready to go home."

Investigators said Duty penned a letter to Wise's mother immediately after the killing, saying, "Well by the time you get this letter you will already know that your son is dead. I know now because I just killed him an hour ago. Gee you'd think I'd be feeling some remorse but I'm not."

While waiting to die, Duty also acknowledged three of his attorneys and his brother and sister-in-law, all of whom witnessed the execution from an adjacent room. "You've all been a blessing," he told them.

The drugs began to flow at 6:12 p.m., and Duty's breathing became labored one minute later. At 6:15 p.m., he appeared to stop breathing and the color began to drain from his face.

"There didn't appear to be any issues with the new drug," Oklahoma Department of Corrections spokesman Jerry Massie said afterward.

Duty and two other death-row inmates had challenged the state's decision to use pentobarbital, arguing it could be inhumane because a person could be paralyzed but still aware when a painful third drug is administered to stop the heart. On Tuesday, a federal appeals court upheld a ruling against the other two inmates. Duty did not take part in the appeal.

Several states have been scrambling since Hospira Inc. - the only U.S. manufacturer of the barbiturate normally used in executions - said new batches of sodium thiopental would not be available until at least January. On Thursday, the company said batches could be available "in the first quarter" of next year.

Executions have been delayed in California, Arkansas, Tennessee and Maryland as a result of protocol changes, including the use of new drugs, said Richard Dieter, executive director of the Death Penalty Information Center. In Ohio and Washington, laws were passed to allow for the use of sodium thiopental alone, he said.

But Oklahoma's law calls for the use of a fast-acting barbiturate to be administered first, which gave the state the flexibility to use pentobarbital, Massie said.

Duty pleaded guilty to first-degree murder in the 2001 slaying of Wise. At the time, Duty was serving three life sentences for rape, robbery and shooting with intent to kill.

According to court records, Duty convinced Wise he could get some cigarettes if Wise pretended to be his hostage so that Duty could be transferred into administrative segregation. Wise agreed to let Duty bind his hands behind his back. Duty then strangled him with a sheet, court records state.