Lawyers for an Alabama Death Row inmate set to be executed in November said the state’s process for nitrogen hypoxia executions “is a set of suggestions and customs, changeable at any time,” and asked a federal judge to halt an execution set for this fall.

Carey Dale Grayson, 49, will be put to death on Nov. 21 at William C. Holman Correctional Facility in Atmore. He’s set to be the third execution this year using nitrogen gas.

The first was Kenneth Smith. Smith was executed in January and was the first nitrogen hypoxia execution in the country. The execution quickly became controversial, with Smith writhing on the gurney for several minutes.

In to court records filed late Tuesday, Grayson’s lawyers asked a federal judge for a preliminary injunction barring the state to execute Grayson.

“Rather than investigating what went wrong—as other states have done following issues with executions—(Alabama has) chosen to ignore clear and obvious signs the current protocol contains major problems that will result in more unconstitutionally torturous executions if it continues to be employed,” new court filings say.

“Alabama’s present method of using nitrogen for executions does not work the way (the state) claim(s), and carries an unacceptable risk of conscious suffocation, in violation of the Eighth Amendment.”

The lawyers said the state has made “unwritten alterations” to the heavily redacted protocol, doesn’t use qualified people throughout the procedure to monitor medical equipment, and haven’t revealed what they conceded in a confidential settlement with another prisoner earlier this month.

“In other words, this is hardly a protocol. It is a set of suggestions and customs, changeable at any time, and neither this Court nor Mr. Grayson knows exactly what Defendants will do when executing Mr. Grayson.”

Attorneys representing the state have said Smith held his breath for several minutes after the nitrogen began to flow through his gas mask, causing the physical reaction.

Grayson’s lawyers included Smith’s autopsy report in court filings. Their medical expert, a longtime anesthesiologist, read the autopsy and concluded Smith suffered from negative pressure pulmonary edema. According to the expert, that condition occurs when “inspiration is attempted against an upper airway obstruction, leading to fluid being drawn from blood vessels into the alveoli.”

That conclusion “support(s) the conclusion Mr. Smith was suffocated while conscious, in violation of the Eighth Amendment,” the lawsuit says. The state’s process for nitrogen executions “creates a risk of unconstitutional pain,” the expert said.

The autopsy notes Smith’s lungs did have evidence of fluid and blood.

Grayson’s lawyers, along with lawyers for Alan Miller– who is set to be executed using the same method in September– have argued Smith’s mask didn’t fit properly, allowing oxygen to seep in. Grayson’s lawyers said in court records the mask “did not work as (the state) represented…”

“It does not inherently produce an airtight seal,” said Grayson’s lawyers Tuesday. “It must be fitted to the person wearing the mask and tested as dictated by the manufacturer. That is critically important because, when oxygen leaks into the mask during the execution, breathing air comes into what is supposed to be a closed system, prolonging the execution, and suffocating the prisoner.”

Grayson was convicted with three other men for the brutal Feb. 22, 1994 slaying and mutilation of Vicki Lynn DeBlieux.

His medical expert said, in court records, that the state should do a physical examination of inmates prior to executions to identify any upper airway obstructions that could “inhibit his ability to breathe in the nitrogen gas.” He also said the state should provide some type of pre-hypoxia sedative.

The filing repeats earlier claims that Assistant Alabama Attorney General James Houts is involved in the training for prison officials on using masks. “In fact, the only person (Grayson’s lawyers are) aware that is involved in the training is Assistant Attorney General James Houts, a scuba hobbyist and private pilot employed by Defendant Marshall. His job, crucially, is related to the fit of the mask.”