In the case of Martin v. Ohio, the U.S. Supreme Court upheld a ruling that allowed evidence of self-defense to be used by defendants in murder trials as an affirmative defense while also being required to prove their innocence beyond reasonable doubt. The court ruled 6-3 in favor of this decision, rejecting arguments that it violated due process rights under the Fourteenth Amendment. The case involved Patricia Martin who was convicted for murdering her husband after enduring years of abuse from him and claimed she acted out of self-defense during his attempt to attack her again. Her conviction was initially overturned by an appellate court but later reinstated by the Ohio Supreme Court which held that although she had presented evidence supporting her claim, it did not outweigh prosecution's proof beyond reasonable doubt about her guilt.

In the dissenting opinion for Martin v. Ohio, Justice Powell argued that the majority's decision undermined a fundamental principle of criminal law: that the state bears the burden of proving every element of an offense beyond reasonable doubt. He contended that by allowing Ohio to require defendants to prove self-defense by a preponderance of evidence, it effectively shifted part of this burden onto them. This was particularly concerning in cases where self-defense negated elements like intent or malice aforethought which are crucial for convictions such as murder. The justice also expressed concern about potential confusion among jurors who had to consider both prosecution and defense evidence simultaneously but apply different standards (beyond reasonable doubt vs preponderance). Finally, he noted inconsistencies with previous rulings on similar issues and warned against setting dangerous precedents.