MONTGOMERY, Ala. (AP) — Alabama could be ready to use a new, untried execution method called nitrogen hypoxia to carry out a death sentence as soon as next week, a state attorney told a federal judge Monday.

James Houts, a deputy state attorney general, told U.S. District Judge R. Austin Huffaker Jr. that it is “very likely” the method could be available for the execution of Alan Eugene Miller, currently set for Sept. 22, if the judge blocks the use of lethal injection. Houts said the protocol “is there,” but said the final decision on when to use the new method is up to Corrections Commissioner John Hamm.

Nitrogen hypoxia, which is supposed to cause death by replacing oxygen with nitrogen, has been authorized by Alabama and two other states for executions but has never used by a state.

The disclosure about the possibility of using the new method came during a court hearing on Miller’s request for a preliminary injunction to block his execution by lethal injection. Miller maintains prison staff lost paperwork he returned in 2018 that requested nitrogen as his execution method rather than lethal injection. The Alabama attorney general’s office argued there is no corroborating evidence that Miller returned the form.

Huffaker heard testimony and arguments during an evidentiary hearing in Montgomery federal court. He noted the “high stakes” involved with a looming execution date, but did not immediately rule on the request to block the lethal injection.

When Alabama approved nitrogen hypoxia as an alternative execution method in 2018, state law gave inmates a brief window to designate it as their execution method.

Wearing a maroon shirt and with his hands shackled in front of him, Miller testified that he returned a state form selecting nitrogen on the same day it was distributed to inmates by a prison worker.

“I remember the guy yelling he was going to put something in the door and would be back to pick them up,” Miller testified. He said he signed the form and placed it in the “bean hole” — the prison nickname for the cell door slot used to pass mail, food trays and paperwork — but he did not see who collected it. Miller said he yelled that he wanted the form copied and notarized, but he did not get that.

Miller described how he disliked needles because of painful attempts at drawing blood. He said nitrogen gas sounded like the nitrous oxide gas used at dentist offices, and that seemed better than lethal injection.

“I did not want to be stabbed with a needle,” Miller said.

Houts, attempting to cast doubt on the inmate’s story about the form, asked him if he could describe anything about the officer who distributed the paper, but Miller said he couldn’t.

“I think we are very much entitled to question his veracity,” Houts told the judge.

Alabama told a federal judge last year that it has finished construction of a “system” to put condemned inmates to death using nitrogen gas, but did not give an estimate of when it would be put to use.

Miller’s lawyer, Mara Klebaner, said the state had asked if Miller would waive his claims if nitrogen was ready, but she said they need more information about the nitrogen process. Miller’s lawyers don’t want him to be the test case for an untried execution method, she said.

Klebaner said the Alabama attorney general’s office recently withdrew an execution date request for another inmate after his lawyers provided proof that the inmate had selected nitrogen hypoxia. She said Miller should be treated the same.

The state argued Miller was trying to delay his execution. Houts told the judge the state had gone as far as to see if Miller would agree to be fitted with a mask for use of nitrogen, but the inmate declined. Miller’s attorney said the state presented the gas mask during a deposition and that Miller was understandably upset.

Miller, a delivery truck driver, was convicted in workplace shootings that killed Lee Holdbrooks, Scott Yancy and Terry Jarvis in suburban Birmingham. Miller shot Holdbrooks and Yancy at one business and then drove to another location to shoot Jarvis, evidence showed.

Miller was delusional and believed the men were spreading rumors about him, including that he was gay, testimony showed. A defense psychiatrist said Miller suffered from severe mental illness but his condition wasn’t bad enough to use as a basis for an insanity defense under state law.