Constitutional Limits After Clark

The argument for admission developed in the last section meets its limit in Clark v. Arizona, 548 U.S. 735 (2006), which asks whether a state may take mental-disease and capacity evidence that is freely usable on the insanity defense and bar it when the defendant offers it to show that a required mental state was missing.¹ Clark suffered from schizophrenia and shot and killed a police officer.² The Arizona statute under which he was charged required the State to prove that, in acting to kill the victim, Clark intended to kill a law enforcement officer on duty or knew that the victim was an officer on duty.³ His expert was prepared to testify that his paranoid schizophrenia left him unable to recognize that he was shooting a police officer rather than an alien disguised as one.⁴ Testimony of that kind links a delusion to a fact the offense requires the defendant to have known, the same link that made the evidence relevant in Ruffin earlier in this chapter. The question for the Court was therefore whether Arizona could keep such testimony away from the jury's deliberation on that element.

Arizona's answer came from its own supreme court in State v. Mott, a case about the admissibility of testimony from a psychologist offered to show that the defendant suffered from battered women's syndrome and therefore lacked the capacity to form the mens rea of the crime charged.⁵ The state court held that testimony of a professional psychologist or psychiatrist about a defendant's mental incapacity owing to mental disease or defect was admissible, and could be considered, only for its bearing on an insanity defense. Such testimony could not be considered on the element of mens rea, meaning what the State must show about the defendant's mental state, such as intent or understanding, when the defendant performed the act.⁶ Call this the Mott rule. It channels the evidence to a single issue, and the choice of issue matters because the two issues carry different burdens. A state may place the burden of persuasion on insanity on the defendant, so evidence confined to that defense avails the defendant only if it is persuasive enough to satisfy the burden the defense imposes, while evidence considered on mens rea works against a burden of proof beyond a reasonable doubt that stays with the prosecution.⁷ The rule therefore leaves the evidence in the courtroom but changes the question it can answer and the burden it must overcome to matter.

To see what Clark was challenging, it helps to separate the kinds of evidence that might bear on mens rea. The Court sorted them into three categories: observation evidence, which is what witnesses saw the defendant do and heard him say, including an expert's testimony about his tendencies and behavior; mental-disease evidence, which is opinion testimony that he suffered from a mental disease with features the witness describes; and capacity evidence, which is opinion testimony about his capacity for cognition and moral judgment and ultimately his capacity to form mens rea.⁸ The Mott rule imposed no restriction on the first category and applies to the second and third.⁹ The trial court seems to have applied the restriction to all three categories of what Clark offered, but his objection attacked the Mott rule itself as a violation of due process, whatever kind of witness testified.¹⁰ That claim rested on the presumption of innocence, the presumption of sanity, and the principle that a defendant may present relevant, favorable evidence on an element of the offense.¹¹ The Court rejected the claim and held that the Mott rule does not violate due process.¹²

The decision's reach has two sides, and a reader who sees only one will misapply it. On one side, Arizona's rule survived although it barred the opinion testimony Clark most wanted the jury to weigh on mens rea. States may exclude expert opinion on mens rea while admitting it on insanity, if they so choose.¹³ The Court described the evidence as channeled or restricted to one issue rather than excluded entirely, and it framed the question as whether the reasons for the restriction satisfy the fundamental-fairness standard of due process.¹⁴ On the other side, a state that follows the Model Penal Code and admits the same testimony on mens rea violates nothing, because the Code admits mental-disease evidence whenever it is relevant to a state of mind that is an element of the offense.¹⁵

Hypothetical Illustration

Two states define the same offense, which requires proof that the defendant knew the victim was a security guard on duty. In each state the defendant offers a psychiatrist who will testify that a delusional disorder left the defendant unable to perceive the victim as a guard, along with testimony from neighbors about what the defendant said in the days before the shooting. The first state follows the Model Penal Code, so the psychiatrist's opinion goes to the jury on the knowledge element, where it need only raise a reasonable doubt about what the defendant knew. The second state follows the Mott rule, so the jury may consider the psychiatrist's opinion only on an insanity defense, where the defendant must carry whatever burden that state assigns, while the neighbors' testimony remains available on knowledge. Both rules are consistent with due process after Clark, and a defendant in the second state cannot succeed by pointing to the first state's practice.

The common error is to read the decision as a command, when it permits a state to channel the evidence and does not require any state to do so. The ruling has also drawn the objection that it keeps out highly relevant and reliable evidence, since the same testimony was admissible on insanity in the same case, and that it lowers the government's practical burden of proving that the defendant knew the victim was a police officer.¹⁶ That objection goes to the wisdom of the Mott rule and leaves intact the holding about what due process permits.

The four subsections that follow take the Court's analysis in order. The first three define observation evidence, mental-disease evidence, and capacity evidence one at a time and show how the Mott rule treats each, and the fourth works through the due process reasoning that supported channeling the second and third.

Observation Evidence

The first of the three categories the Court sorted in Clark v. Arizona is observation evidence, meaning testimony from those who observed what the defendant did and heard what he said.¹⁸ The category also reaches testimony an expert witness might give about the defendant's tendency to think in a certain way and his behavioral characteristics.¹⁹ Because the definition looks to what the testimony reports, the Court observed that observation evidence can be presented by either lay or expert witnesses.²⁰

Observation evidence earns its place on the mens rea question for a plain reason. A factfinder infers what was in a person's mind from what the person did and said around the time of the act, and that inference needs no professional to announce that the person was mentally ill. The Court described this evidence as doing two jobs: it may support a professional diagnosis of mental disease, and in any event it is the kind of evidence that can be relevant to show what in fact was on the defendant's mind when he fired the gun.²¹ The record in Clark's case shows the kind of material involved. It covered his behavior at home and with friends, his expressions of belief around the time of the killing that "aliens" were inhabiting the bodies of local people, including government agents, and his driving around the neighborhood before the police arrived.²² Each item is something a witness saw or heard, and the statements about aliens speak directly to what Clark believed about the people around him when he acted.

The next category shows where the line falls. A psychologist who testifies that Clark was psychotic, with a condition within the category of schizophrenia, is giving a diagnosis built from factual reports, professional observations, and tests, which the Court treated as a separate category called mental-disease evidence.²³ Both kinds of testimony may bear on the same element, but they differ in what they report: one describes conduct and words, and the other names a disease. Examinees misplace evidence when they sort it by the witness's credentials, since an expert may give observation evidence just as a lay witness may. The Court also noted that the Mott rule imposed no restriction on considering evidence of this first sort, while the other two categories are taken up in the next two subsections.²⁴

Mental-Disease Evidence

The second category the Court sorted in Clark v. Arizona is mental-disease evidence, which is opinion testimony that the defendant suffered from a mental disease with features the witness describes.²⁶ Observation evidence reports what the defendant did and said, while this category reports a conclusion about the condition that lies behind the conduct. The testimony characteristically, though not always, comes from professional psychologists or psychiatrists who testify as expert witnesses and base their opinions in part on an examination of the defendant, usually conducted after the events in question.²⁷ The qualifier matters because the category is defined by what the testimony asserts, which is a diagnosis, and a professional is simply the usual source of one.

The evidence in Clark's own case shows the pattern. The defense expert's testimony rested on factual reports, professional observations, and tests, and its thrust was that Clark was psychotic at the time in question, with a condition that fell within the category of schizophrenia.²⁸ A diagnosis of that kind is a professional judgment assembled from those inputs and formed after the fact. The jury ordinarily takes the conclusion on the strength of the expert's training and method, whereas with observation evidence the jurors hear what was seen and said and draw their own inferences. That structural difference explains why a state may have reasons for restricting expert opinion about a defendant's mental condition that do not apply to testimony about conduct.

The category matters because the two rules compared in this chapter treat it differently. Under the Arizona rule approved in Clark, mental-disease evidence may be considered on the insanity defense but not on the element of mens rea, because the Mott rule imposed no restriction on observation evidence but applies to this category and to capacity evidence.²⁹ Under MPC § 4.02(1), the same diagnosis is admissible whenever it is relevant to prove that the defendant did or did not have a state of mind that is an element of the offense.³⁰ A psychologist's testimony that a defendant is schizophrenic can therefore reach the jury on the knowledge element in a Code state, while a state following Mott may confine the same testimony to the insanity defense.

The boundary with the next category is where examinees go wrong. In Clark the defense expert also gave an opinion that the symptoms or effects of the disease in Clark's case included an inability to appreciate the nature of his action and to tell that it was wrong.³¹ That testimony no longer names the disease. It describes what the disease did to Clark's capacity for cognition and moral judgment, and the Court treated it as capacity evidence, which the next subsection takes up. Students sort these two kinds of testimony together when they treat a diagnosis and an opinion about incapacity as the same thing, even though both may come from the same expert in the same testimony. The diagnosis alone, that the defendant was psychotic with a condition within schizophrenia, is the mental-disease evidence.

Capacity Evidence

The third category the Court sorted in Clark v. Arizona is capacity evidence, which is opinion testimony about the defendant's capacity for cognition and moral judgment and, ultimately, his capacity to form mens rea.³³ Like mental-disease evidence, it is opinion rather than a report of what a witness saw or heard, and it usually comes from the same professional experts who offer the diagnosis. Its subject is what sets it apart. Where the second category names the disease, capacity evidence concentrates on the specific details of the mental condition that make the difference between sanity and insanity under the state's definition.³⁴ The testimony in Clark shows what those details were, because the experts addressed whether Clark could appreciate the nature of his action and tell that it was wrong.

The experts disagreed on exactly those details. The defense expert gave his opinion that the symptoms or effects of the disease in Clark's case included an inability to appreciate the nature of his action and to tell that it was wrong, while the State's psychiatrist took the view that Clark was a schizophrenic who was still sufficiently able to appreciate the reality of shooting the officer and to know that it was wrong.³⁵ Because both experts described Clark as schizophrenic, the dispute centered on capacity and left the diagnosis as common ground. The two opinions also show that the category is defined by what an opinion addresses. Testimony that the defendant could not appreciate or judge and testimony that he could both qualify as capacity evidence, and the side that calls the witness does not change the label.

Set the defense expert's opinion beside a witness's account of what Clark said around the time of the killing, which the record includes: his expressions of belief that "aliens" were inhabiting the bodies of local people, including government agents.³⁶ The witness reports words Clark spoke, so that account is observation evidence, and the Mott rule imposed no restriction on it. The expert's opinion addresses what the disease did to Clark's ability to appreciate and judge, so it is capacity evidence, and the Mott rule applies to it.³⁷ Both bear on what Clark understood when he fired the gun, yet they differ in kind, since one reports conduct and speech and the other offers a conclusion about capacity. Examinees misfile testimony when they sort it by the side that offers it or by the witness's credentials, because the State's psychiatrist gave capacity evidence too and an expert may give observation evidence.

This category drives the channeling debate because it overlaps the insanity inquiry. An insanity defense turns on the details that separate sanity from insanity under the state's definition, and capacity evidence is the testimony that addresses those details directly. Since the same opinions sit at the center of the insanity defense, a state can argue that they belong on that issue, where the defendant carries the burden of persuasion discussed above, and not on the mens rea element, where the prosecution must prove every element beyond a reasonable doubt. The Mott rule takes that route by leaving observation evidence alone and applying its restriction to mental-disease evidence and capacity evidence.³⁸ A state that follows MPC § 4.02(1) faces no such question, because the Code admits evidence of mental disease whenever it is relevant to a state of mind that is an element of the offense.³⁹ The sorting tells you which testimony the Mott rule reaches. Whether that reach is permissible is a separate step, which the due process subsection below takes up.

Capacity evidence also marks a line that some restrictive jurisdictions draw within mens rea itself. They prohibit mental health evidence offered to show that the defendant lacked the capacity to form a mental state, yet allow it on whether the defendant in fact had the required mental state.⁴⁰ The reasoning follows from how modest a mens rea is: intending an act or knowing a legally relevant fact takes little cognitive capacity, so a mentally abnormal defendant may well fail to form the required state of mind, but rarely because the capacity to form it was missing.⁴¹

The survey of state approaches later in this chapter takes up that line in detail.

Channeling and Due Process

Sorting testimony into observation, mental-disease, and capacity evidence shows which of it the Mott rule reaches, but it does not decide whether the rule is lawful. That question reached the Court in Clark v. Arizona, where the defendant claimed that the Arizona rule violated due process.⁴³ Under the rule, a psychologist's or psychiatrist's testimony about a defendant's mental incapacity owing to mental disease or defect is admissible only for its bearing on an insanity defense and may not be considered on the element of mens rea.⁴⁴ The Court described that arrangement as channeling: the evidence is confined to one issue at trial and is not excluded entirely.⁴⁵ The distinction frames the inquiry, which asks whether the reasons for confining the evidence to that one issue satisfy the fundamental fairness standard of due process.⁴⁶

Clark's challenge drew on three principles, and each marks a place where the rule might have collided with the Constitution. The first is the presumption of innocence, under which the prosecution must prove every element, including mens rea, beyond a reasonable doubt, so that the presumption's force on the mental element is measured by the showing needed to overcome it.⁴⁷ The second is the presumption of sanity, which spares the government from alleging in every charge that the defendant had the capacity to form the mens rea needed for conviction and criminal responsibility.⁴⁸ Unlike the presumption of innocence, the presumption of sanity varies in strength across jurisdictions, and the law has left legislatures considerable leeway to decide what evidence, and how persuasive, is needed to overcome it.⁴⁹ The third is the principle that a defendant may present relevant, favorable evidence on an element of the offense charged.⁵⁰ The first and third push toward admitting the evidence on mens rea, while the second gives the state room to decide how capacity is tested.

The presumption of sanity can be placed in issue at two points, and the Arizona rule keeps only one of them open. A state may let a defendant offer, and a factfinder consider, evidence of mental disease or incapacity for its bearing on the government's burden to show mens rea.⁵¹ Alternatively, the presumption's force may be tested through an insanity defense, where rules such as M'Naghten define the mental differences that excuse a defendant even though the prosecution has proved every element.⁵² The second route carries a different burden, because a state may require the defendant to prove insanity by a preponderance of the evidence or to some more convincing degree, and evidence channeled there avails the defendant only if it is persuasive enough to meet that burden.⁵³ On the mental-state element the roles reverse, since the state still bears the burden of proving every essential element beyond a reasonable doubt, and evidence offered there need only undercut the state's proof.⁵⁴ The channeling dispute is therefore a dispute about which side must persuade the jury of what.

Whether the Constitution forbids that reallocation depends on how firm the third principle is. A defendant has a due process right to present evidence favorable to himself on an element that must be proven to convict, and evidence of mental disease and incapacity is relevant to rebut the government's showing that he in fact formed the required mental state.⁵⁵ The right can be curtailed for a good reason, however, and trial judges may, for example, exclude evidence whose probative value is outweighed by unfair prejudice, confusion of the issues, or potential to mislead the jury, as Holmes v. South Carolina recognized.⁵⁶ From there the state's argument is short: if evidence may be kept out entirely for such reasons, the way it is considered may also be limited, and Arizona claimed that power.⁵⁷ Because the evidence was restricted to one issue and not excluded, the live question became whether the reasons for the restriction satisfy fundamental fairness, and the Court concluded that the reasons supporting the Arizona rule do.⁵⁸

The holding can be stated simply: states may, without violating due process, exclude expert opinion that, because of a mental disorder, the defendant lacked a particular state of mind or the capacity to form mens rea, while admitting that opinion on the insanity defense.⁵⁹ Clark had offered a mental health expert who would testify that his paranoid schizophrenia left him unable to recognize that he was shooting a police officer rather than an alien disguised as one.⁶⁰ Arizona's rule let the jury hear that opinion on insanity and barred it from bearing on whether Clark acted with the required intent or knowledge.⁶¹ Examinees go wrong when they describe the rule as excluding the evidence, because the Court's analysis depends on the evidence remaining available on one issue.

The result fits a wider pattern of deference to state choices about criminal responsibility. In Clark itself the Court observed that history shows no deference to M'Naghten that could elevate its formula to fundamental principle so as to limit "the traditional recognition of a State's capacity to define crimes and defenses."⁶² In Patterson v. New York the Court likewise declined to require States to disprove beyond a reasonable doubt every fact constituting an affirmative defense related to culpability, leaving the subtler balancing of society's interests against the accused's to the legislature.⁶³ In Kansas v. Hendricks the Court noted that legislatures have traditionally defined medical terms that carry legal significance and that legal definitions need not mirror psychiatric ones.⁶⁴ A closer analogy appears in Montana v. Egelhoff, where Montana barred consideration of voluntary intoxication in determining mental state, the Montana Supreme Court held the bar violated due process, and the Supreme Court reversed.⁶⁵ An opinion in that case reasoned that the long history of disallowing intoxication evidence informs what society has understood by a fair opportunity to put forward a defense, though intoxication differs from mental disease, so the case works as an analogy to the Clark question.⁶⁶

Critics of the holding begin from the observation that the same testimony was admissible on insanity in the same case, which suggests it was relevant and reliable enough for a jury to weigh. Restricting it on mens rea then reduces the government's practical burden of proving that the defendant knew he was killing a police officer and so intentionally killed an officer in the line of duty.⁶⁷ The point can also be put as a question about trust: if a jury can handle this evidence on legal insanity, it is hard to see why it cannot handle it on the required mental state.⁶⁸ A defendant named Hector, charged with intentionally killing a police officer, shows the cost. His psychiatrist would testify that paranoid schizophrenia leaves him delusional, convinced that aliens disguised as government agents are trying to kill him, and prone to playing music loudly to drown out voices, while the prosecution would offer a witness who heard him say he wanted to kill police officers and argue that the loud music was a lure.⁶⁹ If the diagnosis may be used only on insanity, the jury deciding intent must set it aside, and the lure theory goes unanswered by the evidence best placed to answer it.

Those who defend restrictions point to practical risks. Admitting psychiatric evidence on mens rea carries the potential for confusing juries and for expert domination of the trial.⁷⁰ Some observers also question the reliability of psychiatric testimony on mental state, given the tendency of experts to tailor their testimony to the party they represent.⁷¹ Those who would admit the evidence answer that careful administration by the trial judge can manage these risks, for example by requiring a proffer outside the jury's presence and deciding whether the testimony has enough scientific support to aid the jury.⁷² These are the objections commonly raised against the evidence on mens rea, and the Court's own detailed reasons for approving the Arizona rule are not set out here.

Nothing in the holding compels another state to follow Arizona. States remain free to exclude the opinion testimony on mens rea while admitting it on insanity if they so choose, which leaves the choice to each state's lawmakers.⁷³ The Model Penal Code makes the opposite choice, admitting evidence of mental disease whenever it is relevant to prove that the defendant did or did not have a state of mind that is an element of the offense.⁷⁴

Hypothetical Illustration

A defendant is charged in two different states with burning an occupied building, an offense requiring knowledge that people were inside. A psychiatrist would testify that a delusional disorder led the defendant to believe the building was an abandoned warehouse. In the state that follows the Arizona approach, the jury hears the testimony on the insanity defense and must set it aside when deciding whether the prosecution proved knowledge, so it helps the defendant only if it persuades the jury that the insanity standard is met. In the state that follows the Code, the jury may weigh the same testimony on knowledge, where it need only leave a reasonable doubt about that element. Both procedures are consistent with due process, because the holding permits the restriction without requiring it.

Exam Analysis Steps

Because the due process question has a fixed order, it is best run as a short sequence whenever an exam fact pattern involves a state restriction on mental-health testimony. The steps are these:

Identify what the state rule does to the testimony, asking whether the evidence is barred from the trial entirely or confined to one issue such as the insanity defense.
Sort the testimony into observation, mental-disease, and capacity evidence, because the Arizona rule restricted only the last two categories.
Recognize that the defendant has a due process right to present relevant, favorable evidence on an element, and that this right yields to a good reason for limiting the evidence.
Ask whether the reasons for the restriction satisfy fundamental fairness, and apply the holding that Arizona's channeling of mental-disease and capacity evidence to the insanity defense does.

The second step is where fact patterns hide the issue. A witness who reports what the defendant said about aliens gives observation evidence that the Mott rule leaves alone, whereas a psychologist's opinion that the defendant could not appreciate the wrongfulness of the act is capacity evidence that the rule restricts.⁷⁵