UN human rights office condemns 'rushed' Arkansas executions

Spokeswoman Liz Throssell stopped short of condemning the move but said: "Rushing executions can deny prisoners the opportunity to fully exercise their right to appeal against their conviction and/or sentence."

Ms Throssell said use of the sedative midazolam "has been criticised for failing to prevent people from suffering pain".

She said the rights office welcomed the stay of execution in four other cases in Arkansas, and pointed to a "welcome and steady decline" in executions in the US in recent years.

The intervention came after Kenneth Williams, 38, was pronounced dead at 11.05pm local time, 13 minutes after his execution began at the Cummins Unit prison at Varner, Arkansas.

An Associated Press reporter who witnessed the execution said Williams lurched and convulsed 20 times during the lethal injection. A prison spokesman said he shook for approximately 10 seconds, about three minutes into the procedure.

Arkansas had scheduled eight executions over an 11-day period before the drug expires on Sunday. That would have been the most in such a compressed period since the US Supreme Court reinstated the death penalty in 1976, but courts issued stays for four of the inmates.

The four lethal injections that were carried out included Monday's first double execution in the US since 2000.

"I extend my sincerest of apologies to the families I have senselessly wronged and deprived of their loved ones," Williams said in a final statement he read from the death chamber. "I was more than wrong. The crimes I perpetrated against you all was senseless, extremely hurtful and inexcusable."

Williams was sentenced to death for killing a former deputy warden, Cecil Boren, after he escaped from prison in 1999. At the time of his escape, Williams was less than three weeks into a life term for the death of a college cheerleader.

"Any kind of movement he had was far less than his victims," said Jodie Efird, one of Mr Boren's daughters, who witnessed the execution.

State officials have declared the string of executions a success, using terms like "closure" for the victims' families. The inmates have died within 20 minutes of their executions beginning, a contrast from midazolam-related executions in other states that took anywhere from 43 minutes to two hours.

The inmates' lawyers have said there are still flaws and that there is no certainty that the inmates are not suffering while they die.

"The long path of justice ended tonight and Arkansans can reflect on the last two weeks with confidence that our system of laws in this state has worked," governor Asa Hutchinson said in a statement issued after the execution. "Carrying out the penalty of the jury in the Kenneth Williams case was necessary. There has never been a question of guilt."

Arkansas Department of Correction has said it has no new source for midazolam, normally a surgical sedative, although it has made similar remarks previously yet still found a new supply.

Williams's lawyers said he had sickle cell trait, lupus and brain damage, and argued the combined maladies could subject him to an exceptionally painful execution in violation of the US Constitution. Arkansas' "one size fits all" execution protocol could leave him in pain after a paralytic agent renders him unable to move, they had argued.

"After the state injects Mr Williams with vecuronium bromide... most or all of the manifestations of his extreme pain and suffering will not be discernible to witnesses," they wrote to the Arkansas Supreme Court, which rejected his request to stop the execution.

The US Supreme Court also denied requests for a stay, including one that argued his claims of intellectual disability had not been fully explored.

Williams was sentenced to death for killing Mr Boren after escaping from the Cummins Unit prison in a barrel holding a mishmash of kitchen scraps. He left the prison - where the execution chamber is located in another part of the facility - less than three weeks into a life term for killing University of Arkansas at Pine Bluff cheerleader Dominique Hurd in 1998.

At the conclusion of that trial, he had taunted the young woman's family by turning to them after the sentence was announced and saying: "You thought I was going to die, didn't you?"

After reaching Mr Boren's house he killed him, stole guns and his truck and drove to Missouri. There, he crashed into a water-delivery truck, killing the driver. While in prison, he confessed to killing another person in 1998.

AP