20 April 2015 :

Oklahoma became the 1st US state to approve nitrogen gas for executions under a measure Governor Mary Fallin signed into law today that provides an alternative death penalty method if lethal injections aren't possible, either because of a court ruling or a drug shortage. Supporters of the new law maintain nitrogen-induced hypoxia is a humane and painless method of execution that requires no medical expertise to perform.
"Oklahoma executes murderers whose crimes are especially heinous," Fallin said in a statement announcing that she had signed the bill into law. "I support that policy, and I believe capital punishment must be performed effectively and without cruelty. The bill I signed today gives the state of Oklahoma another death penalty option that meets that standard."
The bill authored by Republican representative Mike Christian and Republican senator Anthony Sykes had passed the state House on an 85-10 vote and cleared the Senate on a 41-0 vote.
There are no reports of nitrogen gas ever being used to execute humans, and critics say that one concern is that the method is untested. Some states even ban its use to put animals to sleep. But supporters of Oklahoma's plan argue that nitrogen-induced hypoxia - or a lack of oxygen in the blood - is a humane execution method. "The process is fast and painless," said Christian, a former Oklahoma Highway Patrol trooper who wrote the bill. "It's foolproof."
Opponents say there's no way to know whether the method is painless and effective. "It just hasn't been tried, so we don't know," said Represenative Emily Virgin, a Democrat from Norman who opposes the death penalty. The changes come after a botched execution last year in which Oklahoma was using a new sedative as the 1st in a 3-drug combination. State officials tried to halt the lethal injection after the inmate writhed on the gurney and moaned. He died 43 minutes after the process began.
Under the new law, lethal injection would remain the state's 1st choice for executions and nitrogen gas would be its 1st backup method - ahead of the electric chair, which the state hasn't used since 1966, and a firing squad, which has never been used in Oklahoma.