Oklahoma introduced a law allowing it to use nitrogen gas to kill death row prisoners if lethal injections aren't available. Governor Mary Fallin signed into law a bill approving nitrogen as an alternative method of death, giving Oklahoma four different ways to enact its death penalty. The method, which involves pumping a chamber full of nitrogen and leaving a prisoner's body to die from lack of oxygen, has been touted as 'foolproof' by supporters, in the wake of the embarrassingly botched lethal injections. Scroll down for video . Gas chamber: The state of Oklahoma has legalized killing death row in-mates with nitrogen. This 1999 file photo shows an Arizona correctional officer explaining his state's execution method . Executions in the state are currently on hold while the Supreme Court ponders whether the three-drug mix now favored by Oklahoma is constitutional. The pause follows an infamous execution last ear, which saw officials struggle to administer a the poison to an inmate, who writhed on the gurney in pain for some 43 minutes before finally dying. Nitrogen - which has never been used to execute humans before - is now the state's second choice. The new bill, effective from November 2015, moves the electric chair back from second preference to third, while firing squad becomes a distant fourth choice if all other methods are unavailable. Proponents tout that nitrogen killings will be 'fast and painless' for inmates - and also say the method is 'foolproof' as it requires no medical expertise or complex procedures. In a statement issued as the bill was signed, Fallin, a Republican, said: 'Oklahoma executes murderers whose crimes are especially heinous. '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 Rep. Mike Christian and Republican Sen. Anthony Sykes had passed the state House on an 85-10 vote and cleared the Senate on a 41-0 vote. Christian, a former Highway Patrol trooper, said: 'The process is fast and painless - 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 Rep. 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 first in a three-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. Adam Leathers, spokesman for the Oklahoma Coalition to Abolish the Death Penalty, released a statement blasting the new law. 'This is not only a grotesque waste of resources but indicative of a corrupt value system,' he said. 'It is sad to know that our State's collective bloodlust is so unabated that our leadership feels the need to spend resources to put a back up system into place so State sponsored murder can go on uninterrupted.' The problematic execution was blamed on a poorly placed intravenous line and prompted a lawsuit from Oklahoma death row inmates, who argue that the state's new drug combination presents a serious risk of pain and suffering. The U.S. Supreme Court is scheduled to hear arguments later this month. The lack of readily-available lethal injection drugs - and problems with stocks the states do have - has vexed several other states. Utah brought back the firing squad earlier this year in response to a drugs shortage, while Tennessee reinstated the electric chair.
Governor Mary Fallin signed bill allowing nitrogen execution into law . Chamber is pumped full of gas, and body dies from lack of oxygen . Method will become Oklahoma's second choice after lethal injection . Supreme Court is due to rule on whether current execution drugs are legal . If gas execution is not available, state will use electric chair or firing squad .