Some of the most recent disputes have turned on the drug midazolam, which was part of the cocktail that Oklahoma used for the botched execution of an inmate, Clayton Lockett, in 2014.
Gov. Mary Fallin in 2015 signed a measure adding nitrogen gas to the list of execution methods.
After a series of mishaps, Oklahoma has become the first state to use nitrogen gas to carry out an execution.
Executions could resume no earlier than the end of the year.
A grand jury investigating those errors, including the administering of the wrong drug during a 2015 lethal injection, recommended the use of nitrogen gas as an alternative, according to The Oklahoman newspaper. Oklahoma would be the first state to employ the method.
A grand jury investigation sharply assailed officials charged with carrying out Oklahoma's executions, and Scott Pruitt, then the state's attorney general, called them "careless, cavalier and in some circumstances dismissive of established procedures". (Pruitt is now head of the U.S. Environmental Protection Agency.) Multiple prominent officials stepped down during the investigation into the drug mix-up.
In 2014, Oklahoma drew intense scrutiny for its death-penalty procedures after the execution of Clayton Lockett gained worldwide attention.
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In 2014, the execution of Clayton Lockett gained worldwide attention when he kicked, writhed and grimaced for 20 minutes before his execution was called off; he died of a heart attack not long after. An investigation found issues with the IV that was meant to deliver the fatal drugs. "It will be some time, I think, before an execution can be scheduled". If approved, gas inhalation would reportedly be the state's primary execution method.
"As state leaders, it is our duty to find an effective and humane manner that satisfies both the Constitution and the court system", Hunter said.
There's a nationwide shortage of an anesthetic component of a three-part mixture used in some lethal injections.
The House Intelligence Committee has set itself a March 22 deadline to make changes to a draft report authored by panel Republicans, at which point they plan to adopt the report as final and send it on to the intelligence community for any necessary redactions of classified information. Neither state has used the drug in a lethal injection so far.
Hunter noted that nitrogen gas has not been tested as a method of capital punishment - no country uses it for state-sanctioned executions - but that its success has been documented in use with assisted suicides.
Once the protocol is developed, the state must resolve a federal stay on executions before putting it into practice, which could take another five months or more.