1 Cite As: 608 U. S. ____ (2026) Per Curiam Supreme Court of the United States Gary Richard Whitton v. Ricky D. Dixon, Secretary, Florida Department of Corrections
Does a federal court err when it considers post-trial evidence to determine if a state court's finding of "overwhelming evidence" was reasonable? The Court held that a federal court may not consider post-trial evidence that was not presented to the jury when assessing whether a state court reasonably determined that a witness's testimony was immaterial to the jury's verdict.
Vote & lineup delivered the opinion of the Court (1).
⚠ summary flagged: missing/empty section: DISSENT SUMMARY
The question
Does a federal court err when it considers post-trial evidence to determine if a state court's finding of "overwhelming evidence" was reasonable? Specifically, can evidence not presented to the jury be used to assess whether a *Giglio* violation was harmless? This case asks if such evidence can influence the determination of whether a constitutional error affected the jury's verdict.
Petitioner's argument
Petitioner argued that his due process rights were violated under *Giglio v. United States*, 405 U. S. 150 (1972), because a witness provided false testimony about his criminal history. He contended that the Eleventh Circuit erred by relying on post-trial DNA evidence to conclude that the evidence against him was overwhelming. Petitioner sought the granting of his application for a writ of habeas corpus.
Respondent's argument
Respondent argued that petitioner was not prejudiced by any *Giglio* error because the evidence against him was overwhelming. Respondent further contended that petitioner failed to exhaust his *Giglio* claim in state courts. Respondent sought the affirmation of the denial of habeas relief.
The decision
The Court vacated the judgment of the Court of Appeals. It reasoned that the lower court should not have considered post-trial DNA evidence to assess whether the Florida Supreme Court reasonably found that witness testimony was immaterial. Because the DNA evidence was not presented to the jury and did not exist at trial, it could not have influenced the jury's verdict. The Court applied the standard from *Brecht v. Abrahamson*, 507 U. S. 619 (1993), which asks whether a constitutional error had "substantial and injurious effect or influence in determining the jury's verdict." Since the post-trial evidence sheds no light on the jury's actual decision, it cannot be used to evaluate the harmlessness of the error. The Court noted that the Florida Supreme Court did not consider this DNA evidence in its own determination. Consequently, the Court of Appeals was prohibited from using it to evaluate that state court determination. The Court declined to rule on whether the