The spiritual advisor for Kenneth Smith, the Alabama inmate set to die by nitrogen in the first of its kind execution next month, is arguing he is not allowed to lay hands on Smith in his last moments.

Rev. Jeff Hood’s lawyers filed the lawsuit in federal court Wednesday, claiming that the Alabama Department of Corrections’ rule on staying three feet away from Smith during the nitrogen execution is unscientific and violates his right to practice religion.

The lawsuit said the rule is “hostile toward religion,” and is intended to prevent Hood’s ability to touch Smith and pray with him.

The untested execution method is supposed to work by having an inmate inhale pure nitrogen with no source of oxygen. The nitrogen would lead to an inmate losing consciousness, asphyxiating and dying.

Smith is set to be the first to die using the new method. No inmate in the United States has ever been put to death using nitrogen. Smith is scheduled to be executed sometime between 2 a.m. on Thursday, January 25, and 6 a.m. on Friday, January 26.

Smith was twice convicted by juries for the murder-for-hire of Elizabeth Dorlene Sennett in her home in Colbert County in north Alabama in 1988. Sennett, a pastor’s wife, was beaten and stabbed. Smith, who was hired by the husband, confessed to his role in the crime and has been on death row since 1996.

In August, the Alabama Department of Corrections released a redacted version of its protocol for the new method. It revealed that an inmate would inhale the gas through a tightly fitted gas mask.

According to forms signed by Hood and sent to the department, the prison claimed that oxygen sensors would be installed on the execution chamber walls to ensure safety for any officers, spiritual advisors, or other people in the execution chamber. Those forms, obtained by AL.com, state: “However, in the highly unlikely event that the hose supplying breathing gas to the mask were to detach, an area of free-flowing nitrogen gas could result, creating a small area of risk…” The form said that area of risk would be about two feet from the mask.

“Additionally, overpressure could result in a small area of nitrogen gas that displaces the oxygen in the area around the condemned inmate’s face and/or head.”

The lawsuit said Hood hasn’t been given information on how those oxygen sensors are tested, or information on how the execution chamber will be ventilated to ensure nitrogen doesn’t leak from the mask and affect Hood. Gas doesn’t respect boundaries and can’t be expected to only stay within three feet, said the lawsuit.

“However, there is no scientific basis nor was evidence taken during the passage of this legislation or producing the protocol that indicates this ‘safe area’ would make anyone safe,” reads the suit. “Given that nitrogen does not warn of its presence and that it is ambient and can move anywhere in the room, it is unlikely it would stay within the safe area.”

The lawsuit stated there are no safety precautions in place, suggested for workplaces by OSHA or the U.S. Chemical Safety and Hazard Investigation Board, in the nitrogen execution protocol.

The form, titled “Acknowledgment of Spiritual Advisor,” required Hood to agree to remain at least three feet away from the gas mask.

“Dr. Hood has undertaken the necessary steps to be present with Mr. Smith in the execution chamber,” wrote Hood’s lawyers in the lawsuit Wednesday. “This request has been granted. No one, however, has been able to guarantee the safety of the spiritual advisor with this never tested use of a deadly gas in a confined space. He has a right to minister to his parishioner during the direst time of his life. This cannot be done from three feet away demanded in the Acknowledgement of Spiritual Advisor form that Dr. Hood was forced to sign.”

The lawsuit claimed the form is “filled with such vagueness that he is being asked to stay at least three feet from Mr. Smith and cannot lay hands upon him during the execution.”

“In addition to prohibiting touching of Mr. Smith’s head even though he anointed Casey McWhorter’s head with oil in the last execution, these requirements also seem to include, at least in parts the touching of his feet, leg, or arm. Parts of the body that do not explicitly meet the mask or the tube that feeds the nitrogen into the mask but could be construed to be less than three feet away from both leaner and wider interpretations of the ‘nitrogen hypoxia system.’”

Hood’s lawyers asked that the state be barred from executing Smith “until they can do so in a way that does not violate Dr. Hood’s rights” and allow Hood to safely have contact with Smith during the execution.

“Indeed, they deny a prisoner his chosen spiritual advisor’s touch at the most critical juncture of his life: his death.”

Read more: Former sheriff recalls woman’s ‘horrific’ murder-for-hire by pastor as Alabama prepares execution