Washington (AFP) - The US Supreme Court on Monday upheld the use of a controversial sedative in executions by lethal injection, saying it does not violate the Constitution.
In a 5-4 ruling, its five conservative-leaning justices said that the plaintiffs -- death row inmates in Oklahoma -- failed to show that midazolam constituted a "substantial risk of severe pain."
As a result, they said, the drug -- more commonly used in hospitals as a pre-surgery sedative -- does not violate the Constitution's ban on cruel and unusual punishment.
"The prisoners failed to identify a known and available alternative method of execution that entails a lesser risk of pain, a requirement of all Eighth Amendment method of execution claims," said Justice Samuel Alito, who wrote the majority opinion.
The decision was a setback for opponents of capital punishment in the United States, the only Western country that still carries out executions.
Alabama, Arizona, Florida, Louisiana, Oklahoma and Virgina all retain midazolam as an option for use in lethal injections.
Oklahoma Governor Mary Fallin hailed Monday's ruling, saying the Constitution was "clearly not intended to prohibit the death penalty" by lethal injection or use of midazolam.
Oklahoma's attorney general will now tell the state court of criminal appeals that it now can set execution dates for the three death-row plaintiffs.
Death penalty abolitionists expressed dismay, but vowed to carry their cause forward.
- 'Nothing crueler' -
"It's hard to imagine what could be crueler than a prolonged, torturous death, or more unusual," said Diann Rust-Tierney, executive director of the National Coalition to Abolish the Death Penalty.
"The death penalty is on the outs... Yet that message clearly hasn't risen up to the highest court in the land," she said shortly after the ruling.
Dale Baich, a lawyer for the death row plaintiffs, said the decision "contradicts the scientific and medical understanding" of midazolam's properties.
Despite the outcome, Baich said "litigation surely will continue" in hopes of averting "botched executions" in the future.
The Supreme Court, in an April 2008 decision, upheld the constitutionality of execution by lethal injection.
But since then, a refusal by manufacturers -- mainly European -- to supply the required drugs has led states like Oklahoma to seek out alternatives, including midazolam.
In April 2014, Oklahoma death-row inmate Clayton Lockett, convicted of murder, rape and kidnapping, took an agonizing 43 minutes to die and could be seen writhing in pain during his prolonged execution.
A few months earlier, Ohio inmate Dennis McGuire, who murdered a pregnant woman, took 26 minutes to die, while Arizona death row convict Joseph Wood, convicted of killing his ex-girlfriend and her father, took 117 minutes in July 2014.
Lethal injection executions are expected to take 10 minutes, and in all three cases, the men could be seen gasping for air.
- Plaintiff executed -
A fourth plaintiff, Charles Warner, was executed in Oklahoma in January, after the Supreme Court rejected his last-minute appeal for clemency.
On the execution table, Warner -- sentenced to death for raping and killing an 11-month-old girl -- said it felt like his body was "on fire."
Monday's ruling echoed the deep chasm between conservative and liberal Supreme Court justices seen in its historic ruling Friday that made same-sex marriage legal throughout the United States.
"Welcome to Groundhog Day," said Justice Antonin Scalia, who thought the plaintiffs had come to the Supreme Court for clemency "as though clemency were ours to give."
But Justice Sonia Sotomayor said the plaintiffs now were exposed "to what may well be the chemical equivalent of being burned at the stakes."
They should have at least been given a stay of execution, she said, in order for them to prove the "inadequacy" of the drug.
Fellow liberal Justice Stephen Breyer went further, saying it might be appropriate to revisit the question of capital punishment altogether.
"We believe that the time has come for the Court to again consider a more basic question -- whether the death penalty itself is constitutional," he wrote.
US states have executed 17 convicts so far this year, after 35 last year. The numbers have been trending downward since 2009, when 52 executions took place.