Ledell Lee, 51, was executed Thursday after the US Supreme Court rejected eleventh-hour requests to stay the move.
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.
Asa Hutchinson had originally set out a plan to execute eight prisoners before the state's batch of the lethal injection drug, midazolam, expires at the end of April.
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.
He was pronounced dead at 11:56 p.m. local time, four minutes before the warrant for his death was set to expire.
Numerous legal clashes over Arkansas's plan focus on use of the drug midazolam, a sedative meant to render a condemned person unconscious before other drugs induce death.
Ledell Lee, who was convicted of murdering his neighbour in 1993, was put to death just before midnight, with the clock ticking down on two impending deadlines.
The court denied an appeal from Ledell Lee, the other inmate scheduled for execution on Thursday - but his execution, along with all the others on the calendar, is still blocked by a second court ruling. The eight executions would have been the most by a state in such a compressed period since the U.S. Supreme Court reinstated the death penalty in 1976.
As a result, the first three scheduled executions were abandoned because of court decisions.
McKesson Medical-Surgical Inc, a pharmaceutical wholesaler, had argued that it sold Arkansas the drug for medical use, not executions, and that it would suffer harm financially and to its reputation if the executions were carried out. In his first vote on the nation's highest court, newly appointed Justice Neil Gorsuch cast the deciding vote in favor of putting Lee to death.
Legal teams have managed to postpone the execution of three of the men, but three more killings are scheduled at the prison next Monday. Ms Rutledge's office said the Attorney General would not appeal to the US Supreme Court over that case. Breyer repeated his now-familiar refrain that capital punishment itself is unconstitutional, highlighting Arkansas' planned execution spree as evidence. That issue is headed back to the court, with the state planning to appeal an identical restraining order from another judge regarding the state's supply of the drug. While Arkansas Attorney General Leslie Rutledge [official website] released a statement [text] characterizing the execution as bringing closure to Reese's family, Lee had consistently maintained his innocence for years and was seeking DNA tests to prove the same. According to Bloomberg, each of the court's four liberal justices voted in favor of at least one of Lee's requests for a stay of execution.
All those court actions came after the Arkansas Supreme Court had cleared the way for another of the three drugs to be used in the executions.
However, similar suits filed by Lee asking for additional DNA testing were denied.
Past year the number of Americans executed fell to 20, compared to the 98 who were put to death in 1999.
"If the State of Arkansas was able to procure any of our USA -manufactured drugs for use in lethal injections despite these controls - which it will not confirm or deny to us - it was not directly from us, nor with our knowledge", Hikma Pharmaceuticals spokeswoman Brooke Clarke wrote. McKesson did not have an immediate comment on the court allowing its drug to be used.