BONNE TERRE, Mo. (CN) - Missouri cannot put to death a man convicted of killing three people with a hammer since the lethal injection could also trigger a violent seizure, the Supreme Court ruled late Tuesday, granting a stay of execution pending appeal.
Scheduled for execution at 6 p.m. Tuesday, Ernest Lee Johnsonis missing 20 percent of his brain tissue because of surgery he underwent while on death row in 2008 to remove a benign tumor.
Johnson, 55, claims that the execution drug, pentobarbital, could induce painful seizures, but a federal judge in Missouri dismissed his complaint for failure to state a claim.
The U.S. Supreme Court granted Johnson a stay Tuesday pending the Eighth Circuit's consideration of the case.
It is not clear when the appeals court will rule whether Johnson's complaint was properly dismissed for failure to state a claim or whether the trial court should have let the issue proceed to the summary-judgment stage.
Johnson was convicted on three counts of first-degree murder for killing Mary Bratcher, 46; Mable Scruggs, 57; and Fred Jones, 58, during the robbery of a Casey's General Store in Columbia, Mo., on Feb. 12, 1994.
Johnson beat all three to death with a claw hammer, stabbed Bratcher at least 10 times and shot Jones in the face.
He was arrested after police found a bank bag, stolen money and store receipts at his home.
Testing after his conviction revealed Johnson had an IQ of 67, which is considered mentally disabled.
Johnson was on death row when the Supreme Court ruled in 2001 that executing the mentally disabled was unconstitutionally cruel. Johnson had a new sentencing hearing, but was again sentenced to death in 2003. After the Missouri Supreme Court threw that ruling out, Johnson was sentenced to death for a third time in 2006.
Johnson's attorney says his client is prone to seizures and has trouble walking because of the tumor and loss of brain tissue in 2008.
The defense team has a medical expert who says Johnson faces a significant risk for seizures during the execution process because of his brain injuries.
The Missouri Attorney General's Office argued in court filings that the state has carried out 18 rapid and painless executions since going to the one-drug method in November 2013.