Alabama Death Row inmate Alan Eugene Miller said he has no intention of holding his breath or resisting his execution from nitrogen gas suffocation, but he’s worried the state will fail at securing his gas mask because they’re “incompetent.”

“I don’t think ya’ll know what you’re doing,” Miller, who would be only the second inmate in America to die by suffocating on nitrogen gas, told a state attorney during a deposition. “And these guys can’t even open a cell door sometimes. They’re keystone cops is basically what they are.”

The deposition was filed as part of an argument Miller’s lawyers made earlier this week. That filing also said the only training execution team members have for preparing an inmate for the procedure is from an Alabama Attorney General’s Office prosecutor.

Miller, 59, is set to die on Sept. 26 at William C. Holman Correctional Facility in Atmore. The prison is the only facility in the state with an execution chamber and is where most death row inmates are housed.

In a Monday filing in federal court, Miller’s attorneys said Alabama Attorney General Steve Marshall’s office and its deputy, James Houts, are “responsible for training the execution team on how to carry out a nitrogen hypoxia execution.”

Miller said he’s open to having the gas mask fitted to his face prior to his September execution, but only if a doctor, medical professional or third party appointed by a federal judge does the fitting. That’s because he believes the prison workers are “incompetent” at mask fitting.

The execution, if carried out, will be the second using nitrogen in the country. The first was also in Alabama, when the state executed Kenneth Eugene Smith in January. That execution was widely criticized, after Smith convulsed for several minutes on the gurney.

State officials have argued that Smith held his breath at the beginning of his execution, delaying the nitrogen entering his body.

“The best explanation of the testimony is that Smith held his breath and lost consciousness when he breathed nitrogen gas—not that the mask did not fit or that the nitrogen was impure,” the Alabama Attorney General’s Office said in a filing earlier this month.

Miller “has no physiological explanation for how Smith could have suffered due to the State’s nitrogen hypoxia protocol,” it said.

But on Monday, Miller’s lawyers said the state doesn’t offer any proof for their claims. The state “hang(s) their hat exclusively on the self-serving testimony of a witness who claims to have remembered Mr. Smith’s oxygen levels nearly seven months after the execution.”

The execution team captain didn’t write down those oxygen levels, according to Miller’s lawyers, nor tell anyone about them on the night of the execution.

“In fact, evidence in the record suggest that the witness could not even see the levels from his position in the execution chamber, and the execution log from Mr. Smith’s execution… undercuts (the state’s) entire argument,” said the filing.

The captain’s deposition was also submitted in public court records.

That man said his responsibility was fitting Smith with his respirator mask for the execution. “I have not encountered any person for whom the mask did not fit securely and effectively,” he said.

During Smith’s execution, the captain said he watched the “readout for one of the pulse oximeters attached to Smith’s earlobe.”

“For a period of time that was longer than I had expected, I noticed that the pulse oximeter continued to read at a steady rate of 97%-98%. I did not notice whether Smith was breathing or holding his breath during this time.”

The captain said that Smith eventually released a deep breath, and then the pulse oximeter dropped “to the low 40s in a matter of seconds.” After 40 more seconds, he said, the reading dropped to 17%.

“This rapid drop in Smith’s pulse oximeter readings was what I had expected would happen when Smith began breathing nitrogen. After those breaths, Smith’s body did not move again,” he said.

Miller’s lawyers wrote that the captain has no medical or scientific training, and had received no training for fitting gas masks. In the heavily redacted filing, the lawyers wrote that he “has never read the (REDACTED) which provides instructions on the proper fit.”

Instead, the filing said, the captain learned how to prepare inmates from state Deputy Attorney General James Houts.

“Mr. Houts has admitted he is not an expert in nitrogen hypoxia protocols, but nevertheless believes he is qualified to (REDACTED) the State’s nitrogen hypoxia system because he is a ‘private pilot, a master scuba diver,’ and served in the military.”

The filing said Houts, too, has no medical or scientific training.

All notes from the state’s execution log that were included in the filing are redacted.

Miller believes, according to his deposition earlier this month, that the state’s gas mask won’t fit him. Various masks haven’t worked on his face before, Miller said, because he has a large head and face. He’s also unable to wear hats sold to prisoners because “they are too small for his head.”

“I’ve a big old head,” he said in the deposition.

According to his Alabama Department of Corrections inmate summary, Miller weighs 351 pounds.

Miller’s team also argued the state won’t use a mask with an inherent airtight seal or perform a negative pressure test on the mask. They also said the prison system should provide Miller, or anyone about to face a nitrogen execution, a sedative to “reduce the needless suffering that occurs during asphyxiation.”