In Andrew v. White, 604 U.S. ---, No. 23-6573 (2025), a habeas case under 28 U.S.C. 2254, the Court held that "the Due Process Clause forbids the introduction of evidence so unduly prejudicial as to render a criminal trial fundamentally unfair."
It explained, “certain principles are fundamental enough that when new factual permutations arise, the necessity to apply the earlier rule will be beyond doubt.”
The Court further noted that the question for lower courts was whether "the trial court’s mistaken admission of irrelevant evidence was so 'unduly prejudicial' as to render her trial "fundamentally unfair.'"
In answering this question, lower courts "might consider the relevance of the disputed evidence to the charges or sentencing factors, the degree of prejudice [the defendant] suffered from its introduction, and whether the trial court provided any mitigating instructions. The ultimate question is whether . . . the evidence 'so infected the trial with unfairness”as to render the resulting conviction or sentence “a denial of due process.'"
