The execution of a US double murderer took nearly 90 minutes after the team trying to deliver a lethal injection had trouble finding a suitable vein.
Many US states use the lethal injection to execute convicts
Joseph Lewis Clark cried out "It don't work", as Ohio executioners struggled with a collapsed vein.
Curtains were drawn to screen the procedure. Clark finally died nearly 90 minutes after the scheduled time.
An execution was recently postponed in California because of ethical issues surrounding lethal injections.
During Clark's execution at the Southern Ohio Correctional Facility in Lucasville, the team worked for about 25 minutes to find a vein in his right arm, the Associated Press reported.
At one point, a team member rolled up the leg of his trousers to try to find a suitable vein in his right leg, the agency said.
While the technicians tried to find a suitable site, Clark, 57, raised his head off the gurney and told them the procedure was not working.
US METHODS OF EXECUTION
Lethal injection: Authorised in 37 states
Electrocution: In 10 states (sole method in Nebraska)
Gas chamber: In five states (all of which have lethal injection as alternative)
Hanging: Only in New Hampshire and Washington
Firing squad: In Idaho and Oklahoma
Curtains behind a glass panel separating him from the area where witnesses watched were drawn, before being reopened later so they could see him die.
Clark was reportedly heard moaning from behind the curtain.
Prisons spokeswoman Andrea Dean told AP that procedures called for inserting two intravenous lines to carry the lethal chemicals - one in each arm, with one operating as a back-up.
Technicians had finally gone ahead using just one site in Clark's left arm, she said, after determining a vein had collapsed.
"This has never happened," Ms Dean was quoted as saying of the delay.
Clark was pronounced dead at 1126 local time (1526 GMT) on Tuesday.
In February, the execution of killer Michael Morales was postponed indefinitely in California, after prison authorities failed twice within 24 hours to find qualified medics to administer the lethal injection.
Morales is now back on Death Row while the state reviews its policy on how to carry out lethal injections.
In January, the Supreme Court halted the execution of a man in Florida to consider whether chemicals used in lethal injections violated a constitutional ban on cruel and unusual punishment.
Lethal injection - which uses a cocktail of three drugs - is the most widely used method of execution in the US, although some inmates are offered the choice of alternatives like electrocution or the gas chamber.
Thirty-eight of the 50 US states and the federal government permit capital punishment.
Clark was sentenced to death after killing a petrol station attendant and a student during a series of robberies he carried out in 1984.
Ohio reintroduced the death penalty in 1999.