By Heide Brandes
OKLAHOMA CITY (Reuters) - The Oklahoma Senate on Thursday passed a bill that would allow nitrogen gas as an execution method, a measure adopted after the flawed 2014 lethal-injection execution of an inmate whose intravenous line was improperly placed by death chamber staff.
The legislation, approved by the state Senate on a 41-0 vote after being passed by the state House of Representatives on a 85-10 vote in March, is headed to the desk of Republican Governor Mary Fallin. The legislature is led by Republicans.
The measure would allow state authorities to consider nitrogen gas as an alternate method of execution if the U.S. Supreme Court determines in an upcoming case that the state's current lethal injection process is unconstitutional.
The nitrogen method of execution would require an inmate to be placed in a sealed chamber or to wear a special mask. The process would involve slowly replacing oxygen with nitrogen.
State Representative Mike Christian, a Republican who authored the bill, has said the process would be painless for inmates and affordable for Oklahoma.
In January, the U.S. Supreme Court agreed to temporarily block the execution of three Oklahoma inmates who are challenging the state's lethal injection procedure.
The court is due to consider on April 29 whether the state's use of a sedative called midazolam violates the U.S. Constitution's ban on cruel and unusual punishment. The inmates say the sedative does not achieve the level of unconsciousness required for surgery, making it unsuitable for executions.
The state's three-drug process has been under scrutiny since the April 2014 execution of convicted murderer Clayton Lockett. He could be seen twisting on the gurney when an intravenous tube was placed incorrectly in his groin area.
The execution was halted and Lockett died about 45 minutes after it started due to a buildup of lethal injection chemicals in his tissue.
(Additional reporting by Lawrence Hurley in Washington; Editing by Jon Herskovitz and Will Dunham)