Concept

Supplementing M'Naghten

Irresistible Impulse Test

Supplementing M'Naghten

M'Naghten asks about knowledge. Under that rule a defendant is excused when mental disease left him unable to understand the nature and quality of what he was doing or, if he understood that, unable to know that it was wrong.¹ Every part of that inquiry is cognitive, so the traditional reading of the rule treats the defendant's inability to control his behavior or to refrain from the crime as irrelevant. A loss of self-control caused by mental illness, standing alone, provides no defense.² The control test adds a second route to acquittal: a defendant is entitled to be acquitted if, as a result of mental illness, he could not control his actions or conform his conduct to the law.³ Nothing in that route depends on whether the defendant knew what he was doing or knew it was wrong, and the verdict is called for even if he did.⁴ The question here is how the second route sits beside the cognitive test and what changes when a jurisdiction does or does not adopt it.

The reason for adding the second route follows from what a knowledge-only test leaves out. A test that asks only whether reason was disabled excuses the defendant whose understanding failed, but it has nothing to say about the defendant whose understanding is intact and whose ability to act on it is not. That defendant answers every question the cognitive test asks and therefore fails it, even though the illness rather than any choice may account for the act. The control rules rested on the premise that some mental diseases curtail volition while cognition remains unimpaired, and they were meant to widen the defense for exactly those defendants.⁵ Jurisdictions that decline the supplement are guarding against the opposite error. Loss of control is harder to prove than ignorance, because psychiatrists often find it difficult to distinguish an impulse that was not resisted from one that could not have been resisted.⁶ Critics also worried that almost anyone with an antisocial personality could claim that he could not control his impulses.⁷ Some object as well that when a compulsion is strong but short of overpowering, the threat of criminal sanctions matters most, so excusing the defendant gives up the one force that might have held the conduct back.⁸

Hypothetical Illustration

A defendant with a severe mental illness kills a neighbor. The defendant understands that the victim is a person, that the act will end the victim's life, and that killing is a crime. Treatment records and expert testimony show a long struggle against a compulsion to kill, and the expert ties the defendant's inability to stop to the illness. In State A, which applies the right-wrong test alone, the defense fails at the threshold. The defendant knew the nature and quality of the act and knew it was wrong, the evidence of lost control is irrelevant to that test, and the defendant is convicted.⁹

Move the identical defendant, with identical evidence, to State B, which supplements the right-wrong test with the control test. The same evidence now goes to the jury on a second question. If the jury finds that the illness left the defendant unable to control the conduct or to conform it to the law, the defendant is entitled to an acquittal even though the act was understood to be wrong.¹⁰

Nothing about the defendant changed between the two scenes, so the jurisdiction's test is the only variable that moved the result. State A asks the cognitive questions and the evidence of struggle never reaches them. State B adds the control question, and that same evidence becomes the center of the case.

The control test operates as an addition to the right-wrong test and does not replace it. In the District of Columbia the right-wrong test was the exclusive test until 1929, when the court approved the irresistible impulse test as a supplement in Smith v. United States, and Durham v. United States describes that supplement as adopted to avoid exclusive reliance on the right-wrong test.¹¹ Because the two tests are alternatives, the defendant's mental condition need not satisfy both, and satisfying either one produces the verdict.¹² Supplementing therefore never makes the insanity defense harder to win than M'Naghten alone. A dissent in Kahler v. Kansas makes the same point about motive: the states that adopted the volitional test understood it to expand the defense, reaching defendants who knew their conduct was wrong but could not restrain themselves.¹³

Two federal decisions show the questions being posed separately, and they differ in what they illustrate. In United States v. Freeman the Second Circuit noted that its district courts had supplemented M'Naghten with a rule calling for acquittal when a defendant who knew his conduct was wrongful was nonetheless unable to obey the law and alter its course, but Freeman's counsel conceded that the rule had no application, so only M'Naghten governed.¹⁴ The court later described the supplement as little more than a gloss on M'Naghten rather than a fundamentally new approach.¹⁵ Freeman thus shows the control route available but not in play. In Fisher v. United States both questions were put and both came out against the defendant, who knew right from wrong and whose will was capable of controlling his impulses, so he was sane in the usual legal sense.¹⁶

The supplement remains a minority position. A minority of jurisdictions explicitly added the control test to M'Naghten,¹⁷ and the volitional approach remains by far the minority rule.¹⁸ A survey of state law counted three states that pair a full M'Naghten test with a volitional formula, alongside fourteen jurisdictions that follow the Model Penal Code and fold a volitional test and a moral-capacity test into one amalgam, a form taken up at the end of this chapter. Other jurisdictions omit control entirely. The federal statute, 18 U.S.C. § 17(a), excuses only a defendant who, as a result of severe mental disease or defect, was unable to appreciate the nature and quality or the wrongfulness of his acts, and it has no control prong.¹⁹ California rejects irresistible impulse as a test of legal insanity, though expert evidence of compulsion may come in on whether the defendant had a required specific mental state, as a partial rather than complete defense.²⁰ Washington applies M'Naghten strictly and reserves the defense for persons who have lost contact with reality so completely that they are beyond the influence of the criminal law.²¹

Exam Analysis Steps

Because the same defendant can be convicted in one jurisdiction and acquitted in another, the first move on an exam stem is to find the governing test, and the remaining moves follow from it. The steps are these:

Identify which insanity test the jurisdiction applies, since the legal significance of a loss-of-control fact depends entirely on that choice.
If the right-wrong test applies alone, ask only whether mental disease left the defendant unable to know the nature and quality of the act or its wrongfulness, and treat evidence of lost control as irrelevant to that question.²²
If the control test supplements the right-wrong test, run the two routes as separate questions and acquit if either one is satisfied.²³
On the control route, ask whether the illness left the defendant unable to control actions or conform conduct to the law, which is a different question from whether the defendant simply failed to do so.²⁴
If the jurisdiction uses a single combined formula, such as the Model Penal Code's, set this analysis aside and apply that formula instead.

Students most often go wrong at the first step. A fact pattern that describes a struggle against an urge, or a defendant overpowered by compulsion, invites the conclusion that insanity is established, and the temptation is to treat lost control as a defense in every jurisdiction. In a right-wrong-only jurisdiction those facts add nothing. In a supplementing jurisdiction they matter only to the control route, where they must still show an inability to refrain and not merely an urge that went unresisted.

Supplementing M'Naghten

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