Whether the Bright-line Cut-off Rule and the Adversarial Expert Evaluation of Adaptive Functioning Exacerbates Capital Juror Comprehension of the Intellectual Disability

Abstract

This study explores the findings of the Capital Jury Project that intellectual disability cases were unique because jurors had difficulties with the adversarial mental proof and definitions. There was the greatest fall from principle to practice in appreciating the veracity of the diagnoses. Intellectual disability was defined numerically as IQ 50-70. Hall v. Florida (2014) recently clarified that an IQ score should take account of the test’s standard error of measurement (SEM), indicating a range of scores, rather than a fixed number, or bright line rule. The disability is a “condition and not a number” and information about defendant’s social and cultural adaptation may be presented. This article presents the results of an exploratory study of capital juror receptivity to mitigating intellectual disability (ID) evidence in 38 death penalty trials, comparing the trial transcripts and 1990s CJP post-trial juror interviews. The study tests the hypothesis that jurors’ receptivity to capital juror receptivity to mitigating intellectual disability (ID) was limited by their difficulties with the adversarial mental proof and definitions, as well as distractions from extralegal factors, unrelated to the evidence. These include jurors’ premature decision-making and heuristic shortcuts, pro-death bias, and racial prejudice. It also examines whether the bright line cut-off rule exacerbated their understanding of the disability. In Kentucky, a state with the bright line cut-off rule, jurors were confused about a range of IQ scores and intellectual declines during developmental years. “IQ was perhaps not above what we consider a moron? I think they were contending that he had an IQ of 70 or 76 or so, had been tested as high as the 80s I recall.” This life and death dispute over a few points of IQ demonstrates that the bright line cut-off of 70 represents a misleading artificial statistical convention and is part of the “can of worms” and poor psychiatric thinking discussed.