(Adds court filing)
By Jon Herskovitz
Oct 18 (Reuters) - A federal judge in Phoenix will hear arguments this week about resuming executions in Arizona, where a 2014 lethal injection that took nearly two hours raised questions about the state's death chamber protocols and the chemicals it uses to kill inmates.
The case is the latest to challenge the drugs used in many states to execute prisoners, and may wind up putting the issue back for review by the U.S. Supreme Court.
Arizona last year changed its lethal injection procedures following the troubled 2014 execution of Joseph Wood, but lawyers for seven Arizona death row inmates contend new guidelines and drugs will violate U.S. constitutional protections against cruel and unusual punishment.
One issue at the hearing set for Wednesday in U.S. district court will be the sedative midazolam, a valium-like drug critics contend does not achieve the level of unconsciousness required for surgery and is therefore unsuitable for executions.
The drug was used in Wood's execution along with a narcotic, hydromorphone. He was seen gasping for air during a nearly two-hour procedure where he received 15 rounds of drug injections. Lethal injections are supposed to result in death in a matter of minutes.
Under the new protocols, Arizona has listed one mix where it will use midazolam along with a drug that causes paralysis and another that stops the heart. A similar combination was used in Oklahoma, which had a troubled execution where an inmate was seen twisting on a death chamber gurney.
The state said in court papers filed late on Monday it intends to revise its protocols and remove midazolam as an option, pledging not to use it even if it becomes available. It has three other options for lethal injection mixes that do not use the drug in the new protocols.
Lawyers for the inmates contend the source of the drugs and their purity have been cloaked in secrecy, since European makers and U.S. pharmaceutical company Pfizer Inc halted sales of drugs used in executions to prison systems in recent years.
As a result, states have turned to lightly regulated compounding pharmacies that mix chemicals. The few states that have obtained lethal injection drugs since then have kept the names of their suppliers confidential.
The lawyers want to put future executions on hold while the court reviews the protocols.
"Officials in Arizona have fought tooth and nail to protect that secrecy, which, along with the use of an experimental drug combination, only serves to increase the risk of more problematic executions," said Dale Baich, an attorney for the inmates.
The state contends its protocols correct previous problems and it should be permitted to implement capital punishment.
"Victims and state governments have rights and interests, too, including an important interest in the timely enforcement of a sentence and the state's interest to enforce its own laws," David Weinzweig argued on behalf of Arizona at a hearing this year.
Reporting by Jon Herskovitz; Editing by Tom Brown