Case Western Reserve Law Review
The right not to be found guilty of a crime absent proof beyond a reasonable doubt is a powerful right. It can be undermined, however, by rules that at first seem to have little to do with reasonable doubt or with burdens of proof.
In the recent case of Clark v. Arizona, the Supreme Court considered whether states may enact rules that categorically prohibit criminal defendants from offering mental disorder evidence for the purpose of raising reasonable doubt regarding the mens rea element of a charged offense. In Arizona law, mental disorder evidence is inadmissible for the purpose of disproving mens rea unless a defendant is pleading insanity, and mental disorder evidence that is admissible but insufficient to meet the burden of proving insanity—yet is sufficient to raise reasonable doubt about mens rea—simply has no effect.
That Arizona prohibits defendants from using mental disorder evidence to raise reasonable doubt about mens rea means that the prosecution’s burden of proof is effectively lessened. The Supreme Court in Clark acknowledged that Arizona’s rule potentially denies criminal defendants the right to test the prosecution’s case, but the Court seemed determined not to conclude that Arizona’s rule is unconstitutional.
As a general rule, however, in the American system of justice more evidence is preferred to less. This preference is reflected in many federal and state rules of evidence and in the constitutional limitations on the power to enact rules of evidence that effectively deny criminal defendants a fair trial. Because rules like Arizona’s prohibit, for insufficient reasons, criminal defendants from presenting evidence that is helpful and trustworthy, such rules therefore threaten the right to present a meaningful defense.
Dora W. Klein, Rehabilitating Mental Disorder Evidence After Clark c. Arizona: Of Burdens, Presumptions, and the Rights to Raise Reasonable Doubt, 60 Case W. Res. L. Rev. 645 (2010).