Supreme Court to hear US execution drug case
The US Supreme Court is to hear the case of three death row inmates who say the use of the sedative midazolam in executions is cruel.
Their lawyers argue midazolam, one of three drugs used in state executions, presents an unconstitutional risk of pain and suffering.
The drug was used in three executions seen as botched in 2014.
The court had previously decided not to delay the executions of four other prisoners in Oklahoma.
As a result, one execution went ahead on 15 January.
Charles Warner was the first person to be put to death by Oklahoma after the botched lethal injection of Clayton Lockett in April 2014.
On Friday, the court did not say if it would delay the other scheduled executions. Although five votes are needed to grant such a delay, only four are required for the court to take up a case.
In Oklahoma, Lockett's execution was stopped after 20 minutes when one of his veins ruptured, preventing the drugs from taking full effect. He writhed and shook uncontrollably after the drugs were administered, witnesses said.
Ohio has ended its use of the sedative after a prisoner gasped and snorted throughout his 26-minute execution. Another execution in Arizona took two hours.
Lawyers for the three Oklahoma inmates argue midazolam cannot achieve the level of unconsciousness required for surgery and was therefore unsuitable for executions.
They say its use amounts to cruel and unusual punishment.
Without the coma-like sedative effect, Oklahoma cannot ensure the prisoner does not experience intense pain when other drugs are injected to kill, the lawyers contend.
The US constitution bans "cruel and unusual punishment" but the Supreme Court has previously ruled executions are permissible.
After the Lockett execution, Oklahoma increased the amount of midazolam used in executions.
Executions in the US have also been delayed amid problems finding suppliers for the drugs used in lethal injections as many firms have refused to source them.