( KTRS ) Missouri is set to execute a man convicted of beating three people to death with a claw hammer during a robbery in Columbia in 1994.

Ernest Lee Johnson is scheduled to die today and would be the seventh person put to death in Missouri this year. Johnson had part of a benign brain tumor removed in 2008, an appeal to the U.S. Supreme Court claims the tumor and damage, combined with the execution drug, could cause a painful seizure.

A second appeal, to the Missouri Supreme Court, claims Johnson’s life should be spared because he is mentally disabled.

The Missouri Attorney General’s office says both claims are without merit.