ST. LOUIS (AP) — Death penalty opponents plan vigils at several locations around Missouri on Tuesday as the state prepares for its seventh execution of 2015.

Ernest Lee Johnson is scheduled to die at 6 p.m. for killing three Columbia convenience store workers in 1994. An appeal to the U.S. Supreme Court claims the execution drug could cause painful seizures because Johnson still has part of a benign tumor in his brain, and surgery to remove the rest of the tumor in 2008 forced removal of up to 20 percent of his brain tissue. A separate appeal to the Missouri Supreme Court claims Johnson has an IQ of 67 and his life should be spared because he is mentally disabled.

Only Texas, with 12, has performed more executions than Missouri this year.