The U.S. Supreme Court recently engaged in oral arguments for the case concerning Dexter Johnson, a Texas death row inmate challenging his execution based on claims of intellectual disability. This case brings into focus the evolving understanding and diagnostic criteria for intellectual disabilities, as demonstrated in the case Guerrero v. Johnson.
Dexter Johnson was sentenced to death following a 2006 double homicide. During his trial, expert testimony had assessed Johnson’s IQ to be between 74 and 88, categorizing him outside the then-existing diagnostic criteria for intellectual disability. Nevertheless, a significant shift occurred with the publication of the DSM-5 by the American Psychiatric Association in 2013. This edition de-emphasized rigid IQ thresholds, impacting how intellectual disabilities were determined. Texas adopted DSM-5 standards in 2018, setting the stage for the current legal arguments.
Underscoring the legal complexities, the Fifth Circuit ruled in 2025 that Johnson’s claim could proceed, a decision that prompted further contention. The issue revolves around the interpretation of 28 U.S.C. § 2244(b)(2)(A), which permits successive habeas petitions if they rely on a new constitutional rule made retroactive by the Supreme Court. Texas argues that the Atkins v. Virginia ruling—a case prohibiting executions of the intellectually disabled—predates Johnson’s initial petition, asserting that updates to the DSM provide new facts but do not constitute a new rule of law.
During the Supreme Court’s hearing, robust discussions emerged. Justices questioned the applicability of Atkins at the time of Johnson’s original petition. Notably, Justice Elena Kagan and Justice Ketanji Brown Jackson probed whether a rule unavailable for practical use, could truly be considered “available.” The legal discourse zeroed in on whether Congress intended to allow external scientific bodies like the American Psychiatric Association to indirectly influence constitutional law without explicit Supreme Court action.
Justice Clarence Thomas raised critical inquiries about the permanency of Atkins as a new rule, while Justice Brett Kavanaugh highlighted potential concerns about perpetual litigation without closure. Justice Amy Coney Barrett’s hypothetical about future diagnostic manuals sparked debate about the potential implications for future claims, emphasizing the complexities of adapting static legal standards to evolving scientific insights.
This case underscores a broader legal tension between static legal frameworks and the dynamic nature of scientific understanding. The Supreme Court’s forthcoming decision will likely have profound implications for the future of intellectual disability claims in the capital punishment context.