(Reuters) - Missouri on Tuesday plans to execute a man who murdered three people in the robbery of a convenience store in 1994.
Ernest Lee Johnson, 55, is scheduled to die by lethal injection at about 6 p.m. at the state prison in Bonne Terre, Missouri, unless granted clemency by the state's governor or the U.S. Supreme Court agrees to hear his case.
Johnson was convicted of bludgeoning to death Mary Bratcher, Mabel Scrubbs and Fred Jones using a hammer, a screw driver and a gun, according to court records. Defense attorneys have argued in unsuccessful appeals that he has an intellectual disability and is not therefore eligible for execution.
Defense attorneys have petitioned to appeal to the U.S. Supreme Court, on both the disability issue and on the argument that because Johnson has a slow-growing brain tumor, the pentobarbital used in lethal executions in Missouri could cause him to suffer seizures and pain.
Defense attorney Jeremy Weis said that a 2008 surgery to remove Johnson's slow-growing tumor did not get all of it, and that he has had prior seizures. Weis said that a portion of Johnson's brain is missing.
Prosecutors have said in court documents that Johnson's claims are without merit.
Weis said he expects a decision from the U.S. Supreme Court later on Tuesday afternoon.
Missouri Governor Jay Nixon has received and is reviewing Johnson's petition for clemency, spokesman Scott Holste said.
On Oct. 2, Nixon, a Democrat, commuted the sentence of the last man scheduled to die in Missouri, Kimber Edwards, to life in prison.
A total of 25 people have been executed in the United States so far this year, according to the Death Penalty Information Center, including six in Missouri.
Reporting by Mary Wisniewski in Chicago; Editing by Sandra Maler