Arkansas has executed Ledell Lee in the US state's first use of the death penalty in 12 years.
It is the first of a series of executions expected after the state Supreme Court overturned a lower court ruling blocking the use of a lethal injection.
Justices reversed the ban on the use of vecuronium bromide, one of the three drugs used by the state.
He was pronounced dead at 2356 local time on Thursday (0456 GMT on Friday) at the state's death chamber in its Cummins Unit prison, a Department of Corrections spokesman said.
Lee did not make a final statement. Instead of a last meal, he asked to receive communion, an official said.
The state had planned to carry out eight executions in 11 days, before its supply of the lethal injection drug, midazolam, expired on 30 April.
The first three executions were cancelled due to various court rulings.
Lee told the BBC's Aleem Maqbool in a recent interview that he was innocent of the murder of Debra Reese, and death row was like a "living nightmare".
The other inmate due to die on Thursday has been given a stay to make time for advanced DNA testing that his lawyers say could prove his innocence.
Stacey Johnson was convicted of the murder of Carol Heath, who was beaten and had her throat slit in her flat in 1993.
The ruling on Thursday paves the way for the series of executions the state had planned this month.
Like many US states, Arkansas has struggled to find the drugs it needs to carry out executions. Its last was in 2005.
The frenetic filing of lawsuits and appeals in Arkansas has a profound impact on those awaiting execution, on their families and on the relatives of their victims.
The widower of one victim told me that if he had been told from the beginning that his wife's killer would be in prison for life without parole, he might have been able to move on.
But, he said, to have the prospect of the man's execution arise and disappear over the years means reliving the hurt of the murder itself, and that every stay of execution now feels like an insult to his wife.
What this highlights is how hard it has become for states to kill by lethal injection, with botched executions and drug companies saying they do not want their products associated with the practice.