MONTGOMERY, Ala. (AP) — A federal judge on Thursday declined to halt an upcoming nitrogen gas execution in Alabama, stating the inmate was unlikely to succeed on claims that this execution method, previously employed multiple times, is unconstitutionally cruel.

Chief U.S. District Judge Emily Marks turned down Anthony Boyd’s request to prevent his scheduled Oct. 23 execution. Marks noted that Boyd had not satisfied the legal requirements necessary for the “extraordinary remedy of a preliminary injunction.” Boyd’s lawyers are appealing this decision.

Last year, Alabama began executing some inmates using nitrogen gas. This method involves a gas mask to replace breathable air with pure nitrogen gas, leading the inmate to die due to oxygen deprivation.

Boyd, aged 53, argued that the method contravenes the Eighth Amendment because it causes inmates “conscious suffocation” and subjects them to the pain and terror associated with oxygen deprivation. He suggested that a firing squad or an oral mixture of lethal drugs administered by a medical professional would be preferable alternatives.

“The Court does not doubt that a person consciously deprived of oxygen even for two minutes under the Protocol experiences discomfort, panic, and emotional distress,” Marks noted in her decision.

But she added that the U.S. Constitution “does not guarantee Boyd a painless death” and that the fear of impending death is part of every execution.

The ruling followed a hearing last month focusing on how long an inmate remains conscious during a nitrogen execution and elucidating the reasons behind the noticeable shaking and gasping movements seen in those executed by this method.

The protocol requires prison officials to keep the nitrogen flowing for at least 15 minutes or five minutes after monitoring shows the inmate no longer has a heartbeat. The state indicated in court records that the first five inmates executed by nitrogen gas died at times ranging from 16 to 23 minutes after the nitrogen gas began flowing, Marks wrote.

A jury convicted Boyd of capital murder for his role in the 1993 killing of Gregory Huguley in Talladega. Prosecutors said Huguley was burned to death after he failed to pay for $200 worth of cocaine.

A prosecution witness testified as part of a plea deal that Boyd taped the victim’s feet before another man doused him with gasoline and set Huguley on fire.

Boyd has maintained he did not commit the 1993 murder. His supporters have launched a billboard campaign urging the state to halt the execution.