IQ is back in the news with the Supreme Court’s third look at IQ and capital punishment since 2002. On December 10, 2025, the Court will hear arguments in Hamm v. Smith, a case about an Alabama prisoner’s death eligibility that could have broader impacts.
Any ruling that increases the emphasis on subjective judgment — even if it comes from experts — is a recipe for injustice.
The facts of the case are not in dispute. In 1997 while out of prison on a work release program, Joseph Clifton Smith and an accomplice lured a victim to a forest, where they used a hammer and a saw to inflict 35 blunt-force injuries to the victim’s body and left him for dead after robbing him of cash, his boots, and some tools that Smith later pawned. The total financial gain from the crime was $340.
Smith was convicted in 1998 and sentenced to death, though it has yet to be carried out because of two Supreme Court cases. In 2002, the Court ruled (in Atkins v. Virginia) that it was unconstitutional to execute a person with an intellectual disability because it was a form of cruel and unusual punishment that violated the Eighth Amendment. This effectively barred prisoners with IQs below 70 from capital punishment.
In 2014, this prohibition expanded further — in Hall v. Florida — that courts should take into account the margin of error (technically called the “standard error of measurement,” or SEM) and other influences that can make a strict IQ cutoff inaccurate. In practical terms, this means that scoring as high as 75 may still indicate an intellectual disability if the person also has evidence of impairment in childhood and difficulty in daily functioning.
Over the course of his lifetime, Smith has taken an IQ test five times, with scores ranging from 72 to 78, with an average of 74.6. The immediate question for the Supreme Court to consider is how to handle inmates who have taken multiple IQ tests. In its brief, the State of Alabama prefers to focus on the consistency of the scores and the fact that the highest score is outside the range of an intellectual disability (even when considering the SEM). Alabama also argues that the SEM applies in both directions and that it is as likely that a person’s true intelligence level is above their IQ score as it is below.
Smith’s appellate lawyers argue that even a single score in the range of 70 to 75 has a large enough SEM to trigger the likelihood that a person has an intellectual disability. This side also argues that non-test information (like school records and life history) should be given greater weight when there is a dispute about a prisoner’s true level of intelligence. They argue that this is necessary to holistically evaluate all the evidence regarding whether someone has an intellectual disability.
The dispute over IQ scores in the context of capital punishment has reached the Court for the third time because earlier cases left legal and scientific ambiguities unresolved. For Smith’s case, the question of how to synthesize multiple scores is a frequent one for the courts. Because of the lengthy appeals process, administering multiple IQ tests to a prisoner in a capital trial is very common. The brief from Smith’s lawyers includes a table of dozens of cases in which multiple IQ scores were considered; these prisoners took as many as 10 IQ tests over the course of their lifetime.
Unfortunately, testing experts do not have a consensus about how to reconcile multiple IQ scores. One unique problem is that many low-IQ prisoners on death row have a peculiar pattern of IQ decline. Smith’s five scores all within a 6-point range are the exception. Most of the post-Atkins prisoners with multiple IQ scores show a steady decline — up to 40 points! — over the years.
This is a level of decline generally only seen in dementia patients or people with severe brain damage, and yet these prisoners, usually with no new medical conditions, show a precipitous drop in IQ. The most likely explanation is that they are being coached by their lawyers to fail the tests so that it is easier to argue that the prisoner has an intellectual disability that precludes execution. This obvious confounding factor complicates efforts to apply theoretical rules to the practical question of combining IQ scores in death row appeals.
Rather than a rule about combining IQ scores, an amicus brief from the American Psychological Association and other organizations urges the use of holistic clinical judgment in deciding whether a particular inmate has an intellectual disability. This sounds sensible, but in practice it usually results in dueling expert witnesses. While holistic clinical judgment allows for more nuance and the consideration of unique individual characteristics, in this context it has resulted in inconsistent decisions. That inconsistency is why IQ tests are the topic of Supreme Court deliberations again.
Another problem with prioritizing clinical judgment is that it increases the subjectivity of the legal process. IQ tests are not perfect (no psychological test is), and they should never be the sole basis for making an irreversible life decision about a person. But IQ scores are the most objective evidence available regarding a person’s mental competence. This is especially true when the IQ test was administered before a crime occurred — as happened twice for Smith (IQs of 75 and 74) — when there is little motivation to perform poorly on the test. The argument for clinical judgment to take precedence over objective test scores amounts to little more than saying, “Trust the experts.”
Any ruling that increases the emphasis on subjective judgment — even if it comes from experts — is a recipe for injustice and will likely leave the issue unresolved. Moreover, judges dislike ambiguity when applying the law. Because they reduce subjectivity and ambiguity, IQ scores should be the most important component of any ruling on competency for receiving punishment for one’s crimes.
Hamm v. Smith would be interesting if it were solely about combining IQ scores. However, some of the amicus briefs urge the Court to take a broader view of the case and use it to rule on more general legal principles. One brief filed by Kentucky states that the Atkins rules are unworkable. In that state, appeals based on Atkins have delayed executions so much that the state has been unable to execute anyone since 2008. For these reasons, Kentucky asked the Supreme Court to “engage in a more wholesale rethinking of its Atkins jurisprudence” and to create “clear rules that will allow state courts to predictably and efficiently adjudicate intellectual-disability claims.” The brief comes as close as possible to asking the Court to eliminate the Atkins guidelines without using the word “overturn.”
Even more sweeping is a brief filed by 19 states which argues that Atkins and Hall are part of a larger body of Eighth Amendment case law based on poor legal reasoning that should all be re-evaluated. Because this body of law was used to eliminate life sentences for juvenile criminals and capital sentences for rapists (among other punishments), taking this argument to its logical endpoint could have major consequences for the criminal justice system.
Predicting how the Supreme Court is going to rule is always risky. On the one hand, a lack of scientific consensus regarding how to combine multiple IQ scores may make the justices hesitate to place this decision in the hands of the legal system. On the other hand, the current Court has been skeptical of experts in cases like United States v. Skrmetti and Dobbs v. Jackson Women’s Health Organization.
The Roberts Court is a stickler for the principle of constitutional avoidance, which will make them averse to a sweeping re-interpretation of the Eighth Amendment. But this tendency has its limits; the Court in recent years has shown no hesitation in overruling major cases that it believes were decided incorrectly (e.g., Bakke, Korematsu, Roe) or that created unforeseen problems (Chevron).
A ruling that gives states power to determine guidelines for whether an intellectual disability disqualifies an inmate from execution — and how that is determined — would allow the court to sidestep the pleas for clear guidelines when the scientific community has no clear guidelines to provide. Punting to the states would satisfy the conservative justices’ appetite for federalism by putting future disputes about IQ and capital punishment in the hands of state courts and legislatures. That would make it more likely that Hamm v. Smith would be the last time that the Supreme Court must deal with this issue. Perhaps the third time is the charm for SCOTUS.
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Dr. Russell T. Warne is a research psychologist who has published dozens of scholarly articles and a book about IQ and human intelligence. He currently works as the Chief Scientist for RIOT IQ and is the creator of the Reasoning and Intelligence Online Test. Readers interested in Dr. Warne’s work can find his professional website at https://russellwarne.com and follow him on social media on Facebook and X.
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