The Supreme Court ruled in 2002 that it is unconstitutional to execute people who are mentally retarded, saying those defendants “face a special risk of wrongful execution.” The decision left it up to individual states to decide what level of proof defendants must show of their mental capacity.

The 52-year-old Hill will also be the first inmate in Georgia to be executed using a single drug, rather than a three-drug mix the state has previously used. He was originally set to die last week, but the state delayed the execution because of the change in drugs.