The U.S. Supreme Court rejected a last-ditch effort to block Louisiana’s first execution using nitrogen gas, declining to intervene by a 5-4 vote shortly before a man was to be put to death Tuesday evening for a woman's killing decades ago. Louisiana planned to use the new method to carry out the state's first execution in 15 years on Jessie Hoffman Jr., 46. Hoffman was convicted of killing a 28-year-old advertising executive, Mary “Molly” Elliott, in New Orleans, a crime committed when he was 18. Nitrogen gas has been used just four times to execute a person in the U.S. — all in Alabama. Three other executions, by lethal injection, are scheduled this week — in Arizona on Wednesday and in Florida and Oklahoma on Thursday. Hoffman's lawyers had argued that the nitrogen gas method violated the Eighth Amendment's prohibition on cruel and unusual punishment. They also said it infringed on Hoffman's freedom to practice religion, specifically his Buddhist breathing and meditation in the moments leading up to death. However, Louisiana officials maintained the method, which deprives a person of oxygen, is painless. They also said it was past time for the state to deliver justice as promised to victims' families after a decade and a half hiatus — one brought on partly by an inability to secure lethal injection drugs. Attorney General Liz Murrill said she expects at least four people on Louisiana's death row to be executed this year and said “justice will finally be served” by executing Hoffman. Under Louisiana protocol, which is nearly identical to Alabama's, Hoffman is to be strapped to a gurney and have a full-face respirator mask fitted tightly on him. Pure nitrogen gas is then to be pumped into the mask, forcing him to breathe it in and depriving him of the oxygen needed to maintain bodily functions. The gas is to be administered for at least 15 minutes or five minutes after his heart rate reaches a flatline indication on the EKG, whichever is longer. On Tuesday afternoon, a small group of execution opponents held a vigil outside the rural southeast Louisiana prison at Angola, where the state's executions are carried out. Some passed out prayer cards with photos of a smiling Hoffman and planned a Buddhist reading and “Meditation for Peace.” "To us, and I think to most people, suffocating someone to death with a gas is a pretty horrific means of killing a human being, and we unequivocally take a stand against that," said Samantha Kennedy, the executive director of a group called The Promise of Justice. "There are states around us that are what people call the killing states. And I don't think that it's helpful or wise for Louisiana to follow that path," she added.