The US state of Ohio on Thursday put to death a convicted killer via lethal injection, authorities said, sparking controversy over the use of an untested method after supplies of the drug previously used dried up.
Dennis McGuire, 53, who was sentenced to death for the 1989 rape and murder of a pregnant woman, was pronounced dead at 10:53 am (1553 GMT) in Lucasville, a spokeswoman for the Ohio prisons authority told AFP.
The state had said that it would employ the sedative midazolam and the painkiller hydromorphone -- a drug cocktail never before used in a US execution. An official confirmed the use of the mixture to CNN.
Ohio, like many US states, faced a shortage of the anesthetic formerly used in executions after European manufacturers refused to provide the substance for use in carrying out the death penalty.
McGuire's lawyers said he would die of asphyxia in a phenomenon known as "air hunger," inflicting the sort of "cruel and unusual punishment" prohibited under the US Constitution.
But appeals, which went all the way to the US Supreme Court, were rejected.
A federal judge in Ohio, Gregory Frost, said that "the evidence before the court failed to present a substantial risk that McGuire will experience severe pain," according to a court document.
Elisabeth Semel, a University of California Berkeley law professor specializing in the death penalty, recently told CNN that "no one knows exactly how McGuire will die, how long it will take or what he will experience in the process."
Frost dismissed McGuire's appeal on the same grounds as that of Ronald Phillips, another man on Ohio's death row.
Phillips was supposed to be the first man to die under the new procedure, but his execution was rescheduled for July, to consider his request to donate his organs.
McGuire is the third man to be executed in the United States this year. Ohio executed three of the 39 people put to death in the United States last year, according to the Death Penalty Information Center.