Death by Expert: Cognitive Bias in the Diagnosis of Mild Intellectual Disability

Abstract

In Atkins v. Virginia, the Supreme Court held that executing individuals with intellectual disability violates the Constitution. Due to this categorical exemption, the accuracy and reliability of an intellectual disability determination is literally a matter of life or death. We tested the influence of context on mild intellectual disability diagnosis in a sample of 179 people with intellectual disability expertise. We found that experts diagnosed intellectual disability at nearly identical rates in death penalty and disability benefits cases. Men, Republicans, and people who believed intellectual disability is not an excuse for a crime were significantly less likely to diagnose intellectual disability in both types of cases. These findings suggest that in this sample, the facts of the crime did not cause the experts to refrain from diagnosing intellectual disability.

Keywords: intellectual disability, death penalty, expert