A court in Oklahoma has agreed to suspend all executions in the US state for six months, following a botched lethal injection last month that triggered accusations of torture.

The Oklahoma Court of Criminal Appeals on Thursday granted a six-month stay of execution for Charles Warner, who had originally been scheduled to be put to death on the same evening as Clayton Lockett. 

Lockett's faulty execution on April 29 renewed the debate over the death penalty after the convicted murderer and rapist died 43 minutes after the start of a lethal injection and appeared in significant pain. 

He writhed on the gurney, gritted his teeth, lifted his head several times and moaned. Curtains that allow witnesses to view the execution were closed about 16 minutes into the lethal injection.

The director of the state's prison system, Robert Patton, then called off Warner's execution.

After the incident, Warner’s execution was delayed until May 13. He had been sentenced to death for the rape and murder of his girlfriend's 11-month-old baby.

The attorney general's office supported the decision, saying in a filing that "the state will not object to a 180-day stay to allow completion of [Oklahoma Public Safety Department] Commissioner Michael C. Thompson's investigation."

However, it called an indefinite stay "unwarranted".

Under investigation

President Barack Obama, who backs the death penalty for heinous crimes, condemned the "deeply troubling" execution of Lockett.

He has ordered Attorney General Eric Holder, who is seeking the death penalty in the Boston Marathon bombings case, to conduct a policy review of how the death penalty is applied in the US.

States in the US have faced challenges finding execution methods, with more companies refusing to supply drugs for executions.

Thirty-two states still have the death penalty and lethal injection is used in the vast majority of cases, according to the Death Penalty Information Center, a Washington DC-based non-profit organisation.

Thirty-nine people were executed in the US last year, with Texas leading the way with 16 and Oklahoma second with six.

Source: Agencies