The prosecution insisted that Arnold was not a “madman” but a “wicked man.” True, according to testimony, the prisoner was “very much out of the common way of men,” for example, “morose and ill-natured,” keeping to himself, given to outbursts of unprovoked laughter and cursing. “Though he acted like a wicked man, void of reason, you will have little reason to think he acted like a madman.” That the family did not, despite their testimony, regard Arnold as a madman, the prosecution argued, was shown by their frequent appeals to him to improve his life and his relations with others. You don’t try to “reason with” someone you take to be mad (Howell, vol. 16: 724).

Justice Tracy’s instructions to the jury regarding the legal standards for insanity (or “madness”) strongly support the prosecution’s line of argument:

[P]unishment is intended for example, and to deter other persons from wicked designs; but the punishment of a madman, a person that hath no design, can have no example…. [I]t is not every kind of frantic humour or something unaccountable in a man’s actions that points him out to be such a madman as is to be exempted from punishment: it must be a man that is totally deprived of his understanding and memory, and doth not know what he is doing, no more than an infant, than a brute, or a wild beast; such a one is never the object of punishment; therefore, I must leave it to your consideration, whether [the defendant] … knew what he was doing and whether he was able to distinguish whether he was doing good or evil.

(Howell, vol. 16: 764–65)

Unsurprisingly, on these standards, Arnold was found guilty as charged.

Arnold was reprieved by King George II from the death sentence and was instead incarcerated the rest of his life. Prior to the establishment of an official plea of insanity, this sort of reprieve was not uncommon. This tendency is noteworthy because it evidently reflected recognition of something that the law was loath to codify, that malice is insufficient for (full) criminal responsibility.

Tracy’s famous instructions are remarkable in several respects. The conception of madness as complete deprivation of the capacities for “understanding” or for “designs” is absurdly stringent; no historical candidates for a defense on these grounds lack these capacities altogether. Indeed, the standards fail to exempt four-year-old children or even dogs, who obviously pursue goals in view of some understanding of their environment. From their anxiety to punish the wicked, Tracey’s standards simply evade the difficult questions posed by defendants like Arnold, who surely have some sort of capacity to reason and plan. The problem with these defendants is rather that those very capacities are seriously compromised by mental disorder. To contrast malice to madness is to sidestep the question of how to think about cases in which the malice is itself a piece of madness.

Note that Tracy also invokes the age-old standard that, to be competent, a defendant must be “able to distinguish whether he was doing good or evil” (765), as though that were more or less equivalent to the standard of total deprivation. Surely it is not. Many an “infant” with a capacity for some level of reasoning and planning falls short of anything we should call the capacity to distinguish “good from evil.” We will return to this point later.

Hadfield was in several ways a more appealing figure than Arnold. His madness was almost certainly due to the visible brain injuries he suffered while fighting for his country. And his attempt to shoot the king was not animated by hostility. Arnold was in contrast a surly loner who long harbored animosity toward his victim. These differences must have played some role in the verdicts. In any case, these trials employed two very different conceptions of the bearing of mental disorder on criminal responsibility. The total deprivation view is far too severe to do justice to the claims of madness. The argument in Hadfield makes more sense, but it fails to enunciate a broader standard of exculpation.

Subsequent criminal law has attempted to do better but, as we’ll see, to little or no avail. Depending on the temperaments of the juries, both Arnold and Hadfield could well be found guilty under the standards that prevail in 2011 in most English-speaking jurisdictions. What does this tell us about the criminal law?

The Meaning and Purposes of Criminal Law

The insanity defense is an incompetence defense: a claim that the defendant lacks the capacities that are necessary to make his or her criminal conviction just or even intelligible. An account of what those capacities are should fall out of an account of what criminal law is about. Criminal law is the paradigmatic application of coercive political power, and we need to explain why that is a legitimate use of public authority.

Three different kinds of question arise here, one conceptual and two moral. A substantive question of political morality is: what sort of conduct should be criminalized? This depends on two other questions: what does it mean to criminalize conduct (what is it to make something a crime?), and why should we want to do that? These latter questions are important for this essay, because the rationale of criminal defenses, and hence of the insanity defense, depends on how we answer them.

At a minimum, to declare a kind of conduct a crime is to declare that it warrants an official adverse public response. I do not assume that criminalization is conceptually linked to liability to punishment. There are nonpunitive ways of holding people accountable for violations. Further, as some have suggested, conviction itself can be regarded as a limiting case of punishment (Gardner 1953: 193). Clearly to prohibit by law is not merely to publicly proclaim a system of proscriptive norms. Criminalization is a declaration that certain behavior is not to be tolerated, and this implies the liability of violators to coercive responses of some sort. Whatever liability entails, exactly, our question is why successful defenses, and pleas of insanity in particular, show such liability to be inappropriate.

Criminal Law as a System of Deterrence

The first answer builds on an undeniable principle of political morality: that the political community is entitled, indeed obligated, to protect its members from certain dangers to security and liberty. Call this the protective aim. On a very common view, this aim is the overriding rationale of criminal law. Societies might try to pursue this aim without codes of crime and punishment. They might seek to protect their members by systems of moral or religious training or, more ominously, by preemptively incapacitating and manipulating potentially dangerous actors. On the protective view, criminal law is justified if and only if it is a more effective means than alternative practices for achieving our protective aims. Criminal defenses such as the insanity defense are thus to be explained by their contribution to this protective aim.

This is an unsatisfactory explanation of the phenomenon. Defendants who are acquitted of murder on grounds of insanity are typically subject to further protective custody in response to the dangers their disorders are thought to pose. Civil commitment and criminal conviction are thus alternative responses to individuals who are determined to be a threat to security. The judgment that the dangerous mentally disordered defendant is an inapt candidate for criminal incarceration implies that criminal conviction is more than a means to protection.

The protective theory of criminal law is standardly put in terms of deterrence, and in that form the theory is often endorsed by the courts. Those who qualify for the insanity defense are said not to be deterrable; hence they are not rightly subject to the criminal law, in which case we might rely on civil procedures. In R. v. Porter ((1933) 55 CLR 182), Judge Dixon declares that criminal punishment’s “prime purpose is to preserve society from the depredations of dangerous and vicious people” (186). The judge then asks, rhetorically, “What is the utility of punishing people if they be beyond the control of the law for reasons of mental health?” (187). Judge Dixon’s mistake here is to confuse individual with general deterrence; punishing a non-deterrable offender might well have some kind of a discouraging effect on lawbreaking in the general population. (This mistake is (first?) identified in Hart 2008. Note that the same mistake is made by Tracy in the passage quoted above from Arnold.) Furthermore, Dixon’s declaration ignores the fact that deterrability is a matter of degree. It is doubtful that those for whom an insanity defense is appropriate are altogether beyond the reach of deterrent incentives, and once this is acknowledged the implications of the deterrent theory appear less straightforward. How deterrable does an individual have to be?

Despite its evident shortcomings, this doctrine continues its hold on legal practice. Significantly, the deterrent theory fits smoothly with the wild beast test. Brutishness consists in virtual imperviousness to the threat of punishment; that is what “total deprivation” must mean for legal purposes. As we see in Judge Tracy’s instructions, this unresponsiveness is taken as the measure of the capacity to know “good from evil.” The implicit identification of these capacities was also central to William Blackstone’s teachings about the age of criminal liability. Blackstone writes, in the eighteenth century:

A girl of 13 has been burnt for killing her mistress; and one boy of 10, and another of 9 years old, who had killed their companions, have been sentenced to death, and he of 10 years actually hanged; because it appeared upon their trials, that the one hid himself, and the other hid the body he had killed; which hiding manifested a consciousness of guilt, and a discretion to discern between good and evil.

(Blackstone 1766)

Here the capacity to know good from evil is treated as tantamount to the awareness of one’s liability to sanctions, as revealed in efforts to conceal what one has done—tantamount, in a word, to deterrability. This equation is of course absurd, but on the deterrence theory, it is the only interpretation that can capture the traditional standard of “knowing good from evil.”

This peculiar conflation is not just a relic of archaic legal doctrine but persists in important contemporary legal decisions as well. For instance, in Arizona v. Clark (548 U.S. 735 (2006)), the defendant argued that his psychosis, which included the belief that “aliens” pretending to be police officers were out to get him and could only be stopped by bullets, deprived him of the capacity to know that his conduct was wrong.

In rebuttal, a psychiatrist for the State gave his opinion that Clark’s paranoid schizophrenia did not keep him from appreciating the wrongfulness of his conduct, as shown by his actions before and after the shooting (such as circling the residential block with music blaring as if to lure the police to intervene, evading the police after the shooting, and hiding the gun).

(745)

This rebuttal was evidently dispositive, since the state’s argument prevailed.

This reasoning harks back to the wild beast test. Clark was not “devoid of reason” (the capacity to know right from wrong) because he was in principle deterrable, as manifested by his attempts at concealment. The persistence of this astonishing inference goes a long way to confirm the thesis that the law has advanced very little beyond Arnold in its account of criminal competence.

Let’s turn now to the second prominent answer to the question of why mental disorders should be a defense against criminal conviction.

A conspicuous feature of the criminal law is that it speaks the language not (merely) of danger but of culpability, good and evil, right and wrong. This is a textbook commonplace, but it puts its finger on something central to the self-understanding of criminal law and is implicit in the aspiration to distinguish the mad from the wicked. As the court says in Holloway v. United States ((1945 80 U.S. App. D.C. 3, 4, 148 F.2d 665)): “Our collective conscience does not allow punishment where it cannot impose blame” (666). In the same vein, State v. Guido ((1993) 40 N.J. 191, A.2d) cites the stigmatizing role of criminal conviction: “The postulate is that some wrongdoers are sick while others are bad, and that it is against good morals to stigmatize the sick” (45).

Of course, if we take wickedness to be entailed by the fact that a deterrable offender was undeterred, then this second answer reduces to the first. But the theory of criminal conviction as condemnation asserts something more than this. The Model Penal Code of the American Law Institute endorses this theory in its commentary on the insanity defense. The commentary asserts that the line between criminal law and other modes of coercive constraint is the “line between the use of public agencies and force (1) to condemn the offender by conviction, with resulting sanctions in which the ingredient of reprobation is present no matter how constructive one may seek to make the sentence and the process of correction, and (2) modes of disposition in which the condemnatory element is absent, even though restraint may be involved” (American Law Institute 1985: 164). Criminal conviction expresses “reprobation” or “condemnation” of the offender. It is a form of public blame for conduct that has been prohibited by public authority. On this view, convicted criminals are regarded as wrongdoers to whom it is therefore appropriate to respond in these ways. The theory of excuses and exemptions, including the insanity defense, specifies conditions in which those who violate criminal laws nonetheless do not warrant condemnation.

This conception is broadly retributivist in the sense that conviction and sanctions are considered to be intrinsically fitting responses to wrongdoing. Conviction marks off the offender as a citizen in less than good standing, as one who warrants the distinctive form of blame that punishment constitutes. Retributivism is often more narrowly defined as the view that the suffering of the wrongdoer from just punishment is good in itself. In this form, retributivism strikes many people as an unattractive normative position. It is in any case questionable whether aiming at such a putative good is a legitimate function of coercive political power. It is important, therefore, to note that retributivism in the broad sense need not take this form. On a weaker view, the expression of hard feelings by the criminal law is a demand for recognition by the offender of his or her wrongdoing, as well as an affirmation of the rights of the victims. The expression and enforcement of this demand is said to be valuable independently of whatever suffering, if any, it might induce. (For the best worked-out version of weak retributivism, see Duff 2001. For strong retributivism, see Moore 1987. The defense by Ripstein 2009 of a Kantian interpretation of retributivism is more difficult to categorize.)

Criminal Law as a System of Fair Prohibitions