ST. LOUIS — A condemned Missouri inmate faces a potentially “gruesome and painful” execution because of a rare medical condition that compromises the man’s veins and causes multiple tumors in his head and throat, his attorney said Sunday.

Russell Bucklew is scheduled to die by injection Tuesday evening for killing a former girlfriend’s new boyfriend in 1996 in eastern Missouri.

Bucklew, 49, was moments away from execution in May 2014 when the U.S. Supreme Court halted it amid concerns about Bucklew’s medical condition. He suffers from cavernous hemangioma, a rare ailment that causes weakened and malformed blood vessels.

Nearly four years later, the condition has worsened, attorney Cheryl Pilate said.

“Mr. Bucklew’s rare and severe condition creates a very substantial risk of a gruesome execution,” Pilate said.

A panel of the 8th U.S. Circuit Court of Appeals has already refused to stop the execution.