|According to Death Penalty Info.org, there have been 46 executions in the US so far in 2010. [EPA]
A man put to death in Oklahoma for the 2001 slaying of his cellmate is believed to be the first person to be executed using a sedative commonly used to euthanise animals.
John David Duty died shortly after 0000 GMT on Friday at the Oklahoma state penitentiary in McAlester.
A federal appeals court earlier this week upheld a judge's ruling that allowed the state to substitute
pentobarbital for sodium thiopental, an anaesthetic normally used in the state's lethal injection formula.
A nationwide shortage of sodium thiopental led Oklahoma to alter its three-drug cocktail.
Attorneys for Duty, 58, and two other death-row inmates challenged the state's decision to use pentobarbital, arguing during a November federal court hearing that it had not been done before in executions and could be inhumane.
But one anaesthesiologist whose videotaped deposition was played in court testified that the 5,000 milligrams of pentobarbital the state plans to use is enough to cause unconsciousness and even death within minutes.
The 10th US Circuit Court of Appeals on Tuesday upheld a federal judge's ruling against the other two inmates. Duty's attorney did not appeal the judge's ruling, the attorney general's office said.
Experts testified at the November hearing that no other US state uses pentobarbital during executions.
Jerry Massie, spokesman for the Oklahoma department of corrections, and the head of a Washington D.C.-based group that has been critical of capital punishment both said in interviews on Wednesday that they believed Duty is the first inmate in the country put to death using the drug.
"In all my research, I have not seen that (pentobarbital) has been used before in this context," said Richard Dieter, executive director of the Death Penalty Information Center. But, he noted, "Some states don't say exactly what drugs are used and have kept that out of the public eye."
Oklahoma is among several states that have been scrambling after Hospira Inc. - the sole US manufacturer of sodium thiopental - said new batches of the barbiturate would not be available until January, at the earliest.
Hospira has blamed the shortage on problems with its raw-material suppliers. The Federal Public Defender's office declined comment on whether any last-minute appeals were in the works.
Duty was convicted of the December 2001 slaying of 22-year-old Curtis Wise. At the time, Duty was serving three life sentences for rape, robbery and shooting with intent to kill, all dating to 1978.
According to court records, Duty convinced Wise that 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.
Investigators said Duty penned a letter to Wise's mother, Mary Wise, writing, "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."
The McAlester News-Capital also quoted a letter Duty wrote to Richard Hall, Pittsburg County, Oklahoma, assistant district attorney, saying, "You can't say I don’t deserve the death penalty. I've killed another inmate, taken hostages 3 times, and assaulted a guard. Plus other various things to [sic] numerous to mention."
Duty pleaded guilty to first-degree murder.
A judge rejected Mary Wise's request that Duty be sentenced to life in prison without the possibility of parole after Duty told the judge would kill again if he were returned to prison.
Oklahoma's next scheduled execution is January 6.
A moratorium was placed on capital punishment in the US from 1972 - 1976 after a landmark supreme court decision declared the imposition of the death penalty to be unconstitutional as well as "cruel and unusual punishment". Another series of supreme court decisions in 1976 reaffirmed the court's acceptance of capital punishment.
Since 1976, 1,234 inmates have been executed in the US.