A 60-year-old convicted murderer was to be put to death in Oklahoma on Thursday after the US Supreme Court gave the green light despite a series of botched executions in the state.
A lower court had temporarily halted the scheduled execution of John Grant, but the conservative-leaning Supreme Court lifted the stay without comment.
Grant, who is Black, is scheduled to be put to death at 4:00 pm (2100 GMT) at the Oklahoma State Penitentiary in McAlester for the 1998 murder of a prison cafeteria worker.
A federal appeals court stayed Grant's execution on Wednesday over a challenge to the lethal cocktail used to put inmates to death in Oklahoma.
Attorneys for Grant argued that use of the sedative midazolam would constitute cruel and unusual punishment, violating his constitutional rights.
Midazolam was identified as a potential factor in a series of botched executions in Oklahoma, the last of which was carried out in 2015.
A lawsuit challenging Oklahoma's lethal injection protocols is scheduled to go to trial in February 2022, and the 10th Circuit Court of Appeals had put executions on hold pending a ruling in the case.
The Oklahoma attorney general's office asked the Supreme Court to vacate the stay and the nation's highest court did so just hours ahead of Grant's scheduled execution, with just the three liberal justices objecting.
Clayton Lockett, a convicted murderer executed in Oklahoma in April 2014, took more than 40 minutes to die after a drug was injected into muscle tissue instead of his bloodstream.
The wrong drug was used in the execution of Charles Warner the following year and another execution was called off at the last minute when it was discovered that the wrong drug was to have been used again.
Another Oklahoma death row inmate, Julius Jones, a 41-year-old African American man, is scheduled to be executed on November 18 for the 1999 shooting of a white businessman.
Jones has consistently proclaimed his innocence and his case has attracted the attention of celebrities such as Kim Kardashian and Cleveland Browns quarterback Baker Mayfield.
