MONTGOMERY, Ala. (AP) — A federal judge heard testimony Tuesday about what happened during the nation’s first two nitrogen gas executions, weighing whether to allow Alabama to use that method again next month to put an inmate to death.

Attorneys for Carey Dale Grayson are asking a federal judge to issue a preliminary injunction to block the prisoner’s scheduled Nov. 21 execution with nitrogen gas. The attorneys say Alabama officials must make changes to the procure, adding in a court filing that they “have chosen to ignore clear and obvious signs the current protocol contains major problems.”

Alabama is asking the judge to let the execution proceed as planned.

Alabama has carried out two executions with nitrogen gas. Media witnesses, including The Associated Press, described how the inmates shook on the gurney for two minutes or longer, their spasms followed by what appeared to be several minutes of periodic labored breaths with long pauses in between.

The execution method involves placing a respirator gas mask over the inmate’s face to replace breathable air with pure nitrogen gas, causing death by lack of oxygen. The method has generated debate about its humaneness as critics have argued that the state’s execution protocol does not deliver the quick death the state said it would.

Alabama Corrections Commissioner John Q. Hamm testified Tuesday that he was not concerned about how the executions unfolded. He said involuntary movements, including the type of breathing witnessed during the last two executions by nitrogen gas, were expected based on his research.

Testimony was continuing Tuesday afternoon.