Russell Bucklew, an inmate on death row in Missouri, is scheduled to be executed on Tuesday. Prison staff are planning to execute Bucklew using the sedative pentobarbital. Missouri executioners use only one drug, and they inject the sedative in a massive dose to reduce any pain for the inmate.

Now, lawyers are arguing that Bucklew’s rare disease could cause death by sedative to be considered a “cruel and unusual punishment” for the inmate. Cavernous hemangioma, Bucklew’s disease, causes tumors to form in his head, neck, throat and face. He has had the condition his entire life. Lawyers are arguing that the sedative could cause his tumors to burst. If the above scenario occurred, Bucklew would experience a gruesome end. Lawyers say he would likely choke and gag on his own blood and die in excruciating pain.

Bucklew was originally scheduled to be executed in May of 2014, but his lawyers were able to take his “cruel and unusual punishment” argument to the US Supreme Court. They granted a stay to hear out the claims, but the court ruled that the inmate must propose a reasonable alternative to the sedative. In an appeal, lawyers opted for the use of nitrogen gas in Bucklew’s situation. After review, a federal judge ruled that death by nitrogen would not reduce the risk of the inmate’s suffering, so his execution should proceed as normal.

Last week, Bucklew’s lawyers filed another appeal with the US Supreme Court. They are asking the court to spare his life because of the potential of an extremely painful death.