Ever since the Supreme Court ruled that prisoners suffering from “mental retardation” — a now outdated term — could not face the death penalty in the 2002 case Atkins v. Virginia, debates about whether a felon qualifies for execution have often revolved around a single number: an IQ score. On Tuesday, Georgia prisoner Warren Hill was executed for the 1990 beating death of a fellow inmate. His attorneys argued unsuccessfully that his IQ of 70 disqualified him for the punishment. This evening, Texas is set to execute Robert Ladd for beating a woman to death with a hammer in 1996. His attorney has pointed out that Ladd’s IQ of 67 would disqualify him from execution in most other states.
Last May, the Supreme Court built on the Atkins decision by ruling that Florida could not exclusively use a simple IQ cut-off when it determined who was fit for execution. “An IQ score is an approximation, not a final and infallible assessment of intellectual functioning,” Justice Anthony Kennedy wrote, demanding a more holistic approach by medical professionals. “Intellectual disability is a condition, not a number.”
But how did IQ numbers become so central in death penalty cases in the first place? And why, even after the Supreme Court challenged their usefulness, are we still hearing about them?