US Supreme Court denies Alabama's request to carry out nitrogen gas execution

The US Supreme Court has denied an appeal by the state of Alabama to execute a man using nitrogen gas.

Two lower courts had earlier blocked the use of nitrogen gas in executions, finding the method likely violates the US Constitution's ban on cruel and unusual punishment. Alabama then appealed that ruling.

The brief, unsigned order on the Supreme Court's emergency docket did not provide an explanation the decision, but Justices Clarence Thomas, Samuel Alito and Neil Gorsuch dissented, indicating that they would have granted the state's request for execution.

Death by nitrogen hypoxia - when a death penalty inmate is forced to breathe pure nitrogen through a gas mask until they suffocate - was permanently banned by a federal judge this week after experts and witnesses provided testimony during an April bench trial.

The lower court, which reversed a previous decision by an appeals court, found inmates executed by the relatively new form of capital punishment likely experience "severe air hunger and corresponding emotional distress, anxiety, physiological stress, and physical discomfort" before asphyxiation occurs, according to the BBC's US media partner, CBS News.

Alabama filed an emergency order on Thursday, just hours before the scheduled execution of Jeffery Lee, 49, who was to be put to death at 18:00 local time.

Lee was convicted of murdering two people in a 1998 pawnshop robbery and has been on Alabama's death row for more than two decades. A jury recommended that he be sentenced to life in prison, but a judge overturned the jury's decision and sentenced him to death under a since-abolished judicial override procedure.

The state can still seek to put Lee to death using another execution method.