Starke, Fla. ? A death row inmate won a stay from the Supreme Court on Tuesday night about an hour after he was scheduled to be executed for killing a police officer.

Clarence Hill claimed he is mentally retarded and also challenged the state’s use of execution drugs as cruel.

Witnesses had gathered at the Florida State Prison in Starke for the execution, which was put off for more than an hour before word came from the court.

The witnesses were sent home after Justice Anthony M. Kennedy filed paperwork that said Hill’s death sentence would “be stayed pending further order” of the justices.