When Science Changes but the Law Doesn't: The Supreme Court Takes Up Guerrero v. Johnson
How many chances does a person get to raise a claim when the science changes but the law doesn't? The U.S. Supreme Court heard argument on that question on November 4, 2026, in Guerrero v. Johnson (SCOTUSblog).
The background
Dexter Johnson was convicted in Texas in 2007 of capital murder and sentenced to death. At trial, a defense expert put his IQ between 74 and 88 and concluded he was not intellectually disabled under the standards used at the time. So he never raised a claim under Atkins v. Virginia, the 2002 Supreme Court decision that bars executing people with intellectual disabilities.
In 2013 the American Psychiatric Association published a new edition of its diagnostic manual, the DSM-5, which put less weight on strict IQ cutoffs. In 2019 Johnson scored 70 on an IQ test, and an expert found he met the current definition of intellectual disability. He filed a second federal habeas petition raising the Atkins claim. The district court let it go forward and stayed his execution, and the Fifth Circuit affirmed. Texas appealed.
The legal question
Federal habeas law makes it very hard to file a second petition. One narrow exception covers a claim that relies on a new constitutional rule that was "previously unavailable."
Texas argues that Atkins was decided years before Johnson's first petition, so the rule was always available. On this view the new diagnostic manual changed the facts, not the law.
Johnson argues that a rule is only "available" when it can actually be used. His condition didn't change, but until the medical standards changed, Atkins could not protect him.
Each side has support. The federal government and 22 states back Texas, warning that the Fifth Circuit's approach could invite endless new claims. The National Association of Criminal Defense Lawyers backs Johnson, arguing that people need a way back into court when the science behind a case turns out to be wrong.
Why it matters
This case goes beyond the death penalty. Forensic science changes constantly. Bite-mark comparisons, some arson analysis, and older DNA methods have all been questioned or abandoned. If the Court reads "previously unavailable" narrowly, people convicted under outdated science will find it even harder to get back into court. A decision is expected by summer 2027.
If you or a family member is dealing with a conviction, an appeal, or post-conviction relief in Kentucky or federal court, call the Law Office of B.J. Early, PLLC at (270) 447-5540.