Akin Gump summer associate Jered Matthysse has this summary of yesterday’s decision in Clark v. Arizona:

On Thursday, the Supreme Court held by a vote of six to three that due process does not require a State to use both prongs of the M'Naughten insanity test. Rather, a State may adopt an insanity test that focuses solely on moral incapacity. The Supreme Court also upheld Arizona's Mott Rule, which bars mental-disease and capacity evidence short of insanity from offsetting evidence of criminal intent (mens rea). Justice Souter wrote the opinion for the Court in Clark v. Arizona. Justice Breyer filed a partial concurrence and dissent, arguing that the case should be remanded so that Arizona courts can interpret and apply the Court's ruling. Justice Kennedy also filed a dissent.

During the early hours of June 21, 2000, seventeen-year-old Eric Clark, armed with a handgun, circled his pickup truck around a local neighborhood while blaring loud music. After several neighbors called the police, Flagstaff Police Officer Jeffrey Moritz responded to the scene. As Moritz approached the car, several shots were fired and Clark fled the scene. Shortly thereafter, Clark was arrested and charged with first-degree murder for "intentionally or knowingly" causing the death of a police officer. Additional background information is available here.

At trial, Clark asserted a defense of "guilty except insane" under Arizona Revised Statute § 13-502(A), which provides that the defendant must be "afflicted with a mental disease or defect of such severity that the person did not know the criminal act was wrong." The State of Arizona, however, presented evidence that Clark had purposefully circled the neighborhood with the intention of confronting and killing a police officer. The trial court found that Clark had not met his burden by clear and convincing evidence and was guilty of first-degree murder.


On appeal, Clark argued that Section 13-502(A) violates the due process clause of the Constitution because it includes only one of the two M'Naughten insanity test prongs. In addition, Clark contended that the Mott Rule, which bars evidence of a mental defect or illness, short of insanity, that might undermine the State's mens rea evidence, violates due process. In rejecting both arguments, the Arizona Court of Appeals held that there is no constitutional right to an insanity defense and that Arizona law does not allow evidence of a mental disorder short of insanity as an affirmative defense or to negate the mens rea element of a crime. After the Arizona Supreme Court denied Clark's petition for review, the U.S. Supreme Court granted certiorari. A concise summary of oral arguments at the Supreme Court is available here.

Writing for the majority, Justice Souter first lays out the insanity test as established in M'Naughten's Case. The first prong of the test, according to the majority, asks whether a mental defect leaves a defendant unable to understand what he is doing (cognitive capacity). Next, the second prong asks whether a mental disease or defect leaves a defendant unable to understand that his action is wrong (moral capacity). Significantly, the majority interprets the second prong as presenting an "alternative basis" for recognizing a defense of insanity. In doing so, it treats the two prongs of the M'Naughten insanity test as exclusive, rather than mutually dependent.

Having established that the second prong is merely an alternative to the first, the majority takes on Clark's claim that Arizona's elimination of the first prong violates due process. At the outset, it examines the "traditional Anglo-American approaches to insanity," finding four distinct strands. Each of these strands, when combined, "yield a diversity of American standards." This, according to the majority, shows that no particular formulation of the insanity test has "evolved into a baseline for due process" and that due process "imposes no single canonical formulation of legal insanity." The majority therefore upholds Arizona's use of only one M'Naughten prong and rejects Clark's argument that Arizona's insanity test violates some constitutional minimum, noting that cognitive incapacity is simply a subset of moral incapacity within the meaning of the M'Naughten insanity test.

After dispensing with Clark's first claim, the majority then addresses his due process challenge to Arizona's Mott Rule, which prohibits evidence of a mental illness or defect, short of insanity, to counter the prosecution's mens rea evidence. According to the majority, Arizona's Mott Rule survives Clark's due process challenge so long as the restriction satisfies standards of "fundamental fairness" that due process requires. It begins by limiting Mott to mental-disease and capacity evidence, interpreting the rule as not applying to observation evidence. It then finds (in conflict with the dissent) that Clark's claim only involves a challenge to Mott on due process grounds, rather than the trial court's application of the Mott Rule.

Next, the majority notes that the traditional presumption of sanity "varies" across state and federal jurisdictions and that legislatures are given "leeway" in defining the presumption's strength. In addition, the traditional right to introduce relevant evidence "can be curtailed" if there is a sufficiently "good reason" for doing so. Applying this logic, the majority determines that Arizona had "good reason" for doing so because it possesses the authority to define its presumption of sanity and place the burden of persuasion on defendants. Moreover, the Mott Rule serves to avoid juror confusion, juror misunderstanding, and expert testimony on capacity evidence. Finding that the Mott rule does not violate due process, the majority therefore affirms the ruling of the Court of Appeals of Arizona.

In his partial concurrence and dissent, Justice Breyer agrees with the majority's "basic categorization" of evidence related to insanity. Further, he acknowledges that a State may provide for consideration of mental-disease and capacity evidence "solely in conjunction with the insanity defense." However, Justice Breyer dissents from the majority's posture and would remand the case so that Arizona courts could determine whether state law is consistent with the majority's categorization.

In dissent, Justice Kennedy begins by noting that it is unnecessary for him to address Clark's due process challenge to Arizona's one-pronged insanity test. Instead, he admonishes the majority for limiting Clark's second claim to a post hoc evidentiary categorization. The majority, he declares, creates a "restructured evidentiary universe, with no convincing authority to support it," thereby narrowing Clark's challenge "so he cannot raise the point everyone else thought was involved in the case." This, according to the dissent, is "unworkable," "unfair," and "unrealistic."

Justice Kennedy then tackles the issue "everyone else thought was involved in the case""”Clark's evidentiary right to counter the State's mens rea evidence. In doing so, he finds the Mott Rule problematic because it constitutes a categorical exclusion of evidence, no matter how credible or material. Justice Kennedy also argues that Arizona's (along with the majority's) purported reasons for excluding such evidence are "insufficient to support its categorical exclusion." In finding that the Mott Rule has "no rational justification and imposes a significant burden" on defendants, the dissent would reverse the judgment of the Arizona Court of Appeals.

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