Washington:
Two months after a botched execution in Oklahoma, 21 death row inmates in the southern US state filed suit on Wednesday against prison authorities on procedures to put convicts to death.
Oklahoma suspended its executions for six months after the death of convicted killer and rapist Clayton Lockett by lethal injection in a process that took 43 minutes, well over the expected time of a little over 10 minutes.
He was seen writhing in pain in a spectacle that drew widespread condemnation, including from President Barack Obama.
The next execution in the state is set to take place on November 13.
Charles Warner, convicted of killing an 11-month-old baby, had been due to be executed two hours after Lockett and now heads the list of plaintiffs in a suit filed before a federal court in Oklahoma.
In their complaint, the prisoners underline a significant risk that Oklahoma authorities "will attempt to execute the plaintiffs using the same drugs and procedures used in the attempted execution of Clayton Lockett or with similarly untried, untested and unsound drugs and procedures."
They especially condemn the use of midazolam, an anesthetic "incapable of producing a state of unawareness that will be maintained after either of the other two pain-producing drugs, vecuronium bromide (or its substitute) and potassium chloride, is injected."
The US Food and Drug Administration also has not yet approved the use of midazolam as a stand-alone anesthetic.
The lawsuit protests the use of compounded drugs -- mixed by a compounding pharmacy -- in lethal injections.
States that practice the death penalty have relied increasingly on these compounding pharmacies, which lack federal approval, since European drugmakers refused to provide products used to execute inmates.
If they are executed with these drugs, the inmates argued that they will be "subjected to cruel and unusual punishment, in violation of the Eighth and Fourteenth Amendments to the United States Constitution."
The FDA, the lawsuit noted, "does not verify the identity, purity, potency, quality, safety or effectiveness of compounded drugs."
According to preliminary autopsy results, staff in charge of Lockett's execution failed to administer the intravenous injection correctly and, after several failed attempts, punctured the femoral artery.