Missouri executed a convicted murderer on Wednesday after a court turned down his attorney's appeal based on a report that officials had lied over the drugs used in lethal injections.
Earl Ringo Jr. - who killed two people at a restaurant in 1998 - was pronounced dead at 12:31 a.m. Central Time (0531 GMT) at a prison in Bonne Terre, state corrections department spokesman Mike O'Connell said.
Ringo's attorney, Kay Parish, sought a stay of execution, citing a St. Louis Public Radio report that said state officials administered the drug midazolam on every inmate executed since November, in addition to pentobarbital.
The use of midazolam is under scrutiny nationwide after inmates in a series of botched executions in Ohio, Oklahoma and Arizona were given the drug and took longer than is typical to die, showing signs of distress.
The Missouri Department of Corrections says it administers midazolam before executions and not as part of its execution protocol, and on Tuesday the US Court of Appeals for the Eighth Circuit and the US Supreme Court denied requests to stay the execution.
"It should not be lost in the national debate over the death penalty that Earl Ringo Jr. was responsible for the murders of two innocent Missourians. For 16 years he avoided payment for this crime. Tonight he has paid the penalty," Missouri's Attorney General, Chris Koster, said in a statement.
The 40-year-old was the eighth prisoner executed in Missouri in 2014 and the 28th executed in the United States this year, according to the Death Penalty Information Center.
Ringo and an accomplice robbed a Columbia, Missouri restaurant of $1,400 and shot and killed a restaurant manager and a delivery truck driver, according to court documents.
Separately on Tuesday, the federal appeals court heard oral arguments in a long-running lawsuit filed by more than a dozen Missouri death row inmates, including Ringo, challenging the state over its lethal injection protocols.
Texas is also due on Wednesday to execute Willie Tyrone Trottie, 45, who killed two people and wounded two others in a shooting spree after breaking up with a girlfriend.