A federal judge has ordered the Arkansas authorities to conduct an autopsy on the body of an executed inmate whose lawyer described his death as "horrifying," including jerking and convulsions during his lethal injection.
Judge Kristine Baker of the US Court for the Eastern District of Arkansas issued the order late Friday, less than 24 hours after the state executed the 38-year-old convicted multiple murderer Kenneth Williams.
He was the last of four inmates put to death in a week -- the first executions by the conservative southern state since 2005.
Arkansas officials had said the compressed timeline was necessary because the state's stock of a sedative used in the lethal injection, midazolam, was set to expire at the end of April.
In addition to the autopsy, the judge also ordered the Arkansas authorities to preserve blood and tissue samples from Williams's body.
The emergency motion "for preservation of evidence" was filed by Jason McGehee, a death-row inmate who had been scheduled for execution on Thursday.
He and three other prisoners who were also set to die over an 11-day period before the end of this month have won reprieves.
Williams's lawyer Shawn Nolan has said the condemned man suffered during his execution.
"Within three minutes into the execution, our client began coughing, convulsing, jerking and lurching," he said.
Nolan and the American Civil Liberties Union have called for an investigation into whether the execution on Thursday night amounted to death through torture.
He dismissed as a "whitewash" a comment by Arkansas Governor Asa Hutchinson's spokesman that the physical agitation was an "involuntary muscular reaction" caused by one of the drugs.
Many of the legal clashes over the string of executions focused on midazolam, which is meant to render condemned people unconscious before other drugs cause death.
Critics say it does not always adequately sedate prisoners, potentially causing undue suffering.