US death row inmate Clarence Hill has been executed by lethal injection at a Florida state prison, hours after the Supreme Court rejected a final appeal.
Hill's case caused states to review the lethal injection issue
Hill had received a last-minute stay of execution in January.
Judges rejected his final appeal by a 5-4 vote. Hill claimed chemicals used caused pain, violating a constitutional ban on cruel and unusual punishment.
Hill, 48, was executed for the murder of a Pensacola police officer in the early 1980s.
The initial intervention caused states across the country to review the lethal injection procedure.
His case led to a Supreme Court ruling in June, allowing death row inmates to file last-ditch challenges to lethal injections.
No final comment
The ruling came after Hill argued that the chemicals used would cause unnecessary pain and violate his civil rights.
Hill was said not to have made any final comment before being executed.
"I did not see anything that reflected any kind of pain," Robby Cunningham, a spokesman of the Florida Department of Corrections, told the AFP news agency.
"He was very calm all the time, not having a final word, he laid there calmly on the gurney."
Lethal injection is used in all the 38 states which permit capital punishment, except Nebraska which requires electrocution.
The standard method is a combination of three chemicals.