Concept

Why a Product Test Arose

Product of Mental Disease or Defect

Why a Product Test Arose

Before 1954 two tests governed criminal responsibility in the District of Columbia. The right-wrong test comes from English law and was restated in M'Naghten's Case. The D.C. courts approved it in 1882, and it stood alone until 1929, when the court added the irresistible impulse test as a supplement in Smith v. United States.¹ The two tests ask different questions, one about knowledge and the other about will, but each treats a single symptom of mental illness as the measure of excuse. In Durham v. United States the court concluded that the right-wrong test was inadequate as an exclusive criterion because it rests upon one symptom, and that the irresistible impulse test was inadequate too, so a broader test was needed.²

The court's reasoning starts from how modern psychiatry understands the mind. Psychiatry treats the mind as an integrated personality of which reason is only one element.³ If the mind works as a unit, a disease does not confine itself to one faculty, and a legal test that asks about a single faculty gives the right answer only when the illness happens to act through that faculty. The consequence follows from why the law excuses mentally ill defendants in the first place. Blame is withdrawn because the act flowed from the illness rather than from a free choice. A test that screens for one symptom therefore excuses the defendant who displays that symptom and convicts the defendant whose illness reached the same act through a different channel, although the second defendant is no more blameworthy. A disease can work through altered moods, brooding, and other noncognitive disturbances, and a test aimed at knowledge or sudden loss of will never sees them.⁴ A second difficulty comes from naming symptoms in advance. Tests built on a fixed list of malfunctions tend to freeze the law in conventional patterns and make it harder for psychiatric witnesses to appraise new clusters of symptoms that might disable a person just as much.⁵

The D.C. court was not working alone. Dr. Isaac Ray had argued that insanity is established by the whole body of symptoms and never by a single diagnostic sign, and that view shaped the earlier New Hampshire rule asking whether the crime was the offspring or product of mental disease, which the next section takes up.⁶ In 1953 the British Royal Commission on Capital Punishment recommended that M'Naghten be abrogated, and it described both M'Naghten and the irresistible impulse test as narrow and out of step with modern theories of how the mind works.⁷ The two subsections below take each older test in turn, beginning with the right-wrong test, to show exactly which diseased defendants each one leaves convicted and what a causal question adds.

The Right-Wrong Gap

The first of the two older tests falls short because of the single question it asks. In the formulation of M'Naghten's Case, a defendant is excused only if a defect of reason, caused by disease of the mind, left the defendant unaware of the nature and quality of the act or, if aware of that, unaware that the act was wrong.⁹ Both prongs ask what the defendant knew, so the test screens for one mental faculty, cognition, and treats the failure of that faculty as the only route by which illness can reach conduct.¹⁰ The test works as intended for a defendant whose illness destroys awareness of the act. A psychosis that persuades a defendant that a lemon is being squeezed when a spouse is being strangled leaves the defendant ignorant of what the act is, and the knowledge prong excuses.¹¹ The product test excuses that defendant as well, because the delusion produced the act, but the older test had already reached this defendant, so the new test adds nothing here.

The difficulty appears when the illness reaches the act by another channel.

Under the right-wrong test this defendant is convicted. Knowledge of the act's nature and of its wrongfulness is present, so neither prong is met, and the evidence that the disorder drove the conduct has no place in the legal question. The Durham court identified exactly this class of defendant when it observed that the right-wrong test ignores many mental conditions in which conduct is the product of altered moods, brooding, or other noncognitive disturbances.¹² The product test asks a different question about the same facts, namely whether the act would have occurred but for the disorder, and on these facts the psychiatrist's testimony points toward excuse.¹³

The narrowness of the question also shapes the proof. When the only legal question is whether the defendant could tell right from wrong, evidence about mood, motivation, and the course of the illness has no legal home, and the judge or jury decides without information that bears directly on whether the defendant should be held responsible.¹⁴ Psychiatrists testifying inside that frame must also translate a whole clinical picture into the categories of knowing and wrongness, which carry little medical meaning.¹⁵

The criticism targets the test's reliance on a single symptom. Cognitive impairment stays relevant to the product test: the Durham court said the jury's inquiry may include whether the accused did not know right from wrong, acted under an irresistible impulse, or had lost the power of his will, so a failure of knowledge remains one way an illness can produce an act.¹⁶ What the product test gives up is the exclusivity of that route. A common error is to treat the defendant's ability to say the act was wrong as proof that the illness played no part, when that ability answers only the right-wrong question and leaves the causal question open. The second older test, the irresistible impulse supplement, was added to cover loss of will power, and the next subsection shows what it still leaves out.

The Irresistible Impulse Gap

The second older test was added to repair a defect in the first. The right-wrong test asks only what a defendant knew, so it convicts a defendant who understood the act and its wrongfulness but could not stop. In 1929 the D.C. court responded in Smith v. United States by approving the irresistible impulse test as a supplement, on the recognition that a diseased mental condition may deprive an accused of the will power to resist an impulse.¹⁸ The trial charge reviewed in Davis v. United States shows the pairing at work. The jury was told to acquit a defendant who could not distinguish right from wrong or did not grasp the nature of the act, and also a defendant who knew the act was wrong but whose will had been so completely and involuntarily destroyed that his actions were beyond his control.¹⁹ The supplement thus added a second faculty, will, to the first, cognition. It widened the defense, but the widening had a particular shape, and the shape came from the word chosen to name the new category.

The word 'impulse' carries the limit. The Durham court found the label misleading because it suggests only sudden, momentary inclinations, whereas many mental illnesses produce prolonged alterations in mood and motivation that lead to carefully planned acts, and those acts are no less the product of disease.²⁰ The same court later repeated the point in Carter v. United States, observing that 'impulse' connotes suddenness while many recognizable diseases of the mind involve slow deterioration, brooding, depression, and constant pressure.²¹ The reason this matters comes from how such a test operates in a courtroom. If the question is whether the defendant was overcome by a sudden urge, the facts a jury naturally weighs are the signs of suddenness, and weeks of preparation look like the opposite, the picture of a person in control.

That inference produces the gap. A defendant whose illness gradually reshaped his motives and then drove a deliberate plan falls outside the supplement, even though the illness caused the act as surely as a sudden compulsion would have. The illnesses that most thoroughly rework a person's choices therefore become the least likely to excuse. Two further weaknesses compound the problem. As commonly applied, the control inquiry is framed as a complete destruction of the governing power of the mind, an absolute standard that parallels the total cognitive incapacity the right-wrong test demands.²² And psychiatrists have long doubted that irresistible impulses can be identified as a distinct condition, while a diseased mind may prepare a crime coolly and carefully.²³

Hypothetical Illustration

For two years a defendant has suffered from a delusional disorder that convinces him his business partner is secretly plotting to destroy his family. Over several weeks he studies the partner's schedule, buys supplies, and carries out a calm, detailed plan to attack the partner. He understands that the attack is a crime and that others would condemn it, and he never feels a sudden surge of urge, only a settled conviction fed by the delusion. A psychiatrist testifies that without the disorder he would never have formed the plan. The right-wrong test is not met because he knew the act was wrong, and the control supplement fits poorly because the evidence shows deliberation rather than a sudden loss of control. Under the product test the planning is simply the form the illness took, and the jury asks whether the attack would have occurred but for the disease. On this testimony the answer is yes.

Now change one fact. A second defendant plans a robbery for weeks with the same care, to get money. She carries an unrelated anxiety disorder, but the robbery has no connection to it, and the psychiatrist agrees she would have robbed the store anyway. The planning is identical, yet the product test returns a conviction, because the act would have occurred without the illness.

The product test removes the suddenness assumption by changing what the jury is asked. The supplement examines the form of the act, whether it arrived as an overwhelming urge, while the product test examines its source, whether there is a relationship between disease and act that justifies a reasonable inference that the act would not have been committed but for the disease.²⁴ Under that question, planning is neither required nor disqualifying. Careful preparation can be evidence that the illness shaped the act, as in the first defendant's case, or it can show only that the defendant meant to commit an ordinary crime, as in the second. Students lose this issue when they treat deliberate planning as proof of control, since the same planning appears on both sides of the line and causation is what separates them.²⁵

The older route is not discarded. The Durham court said the jury's inquiry may include whether the accused acted under an irresistible impulse or had lost the power of his will, so a defendant who really was overcome by a sudden compulsion can still show that the disease produced the act.²⁶ What the product test drops is the assumption that only that sudden form qualifies. A separate criticism of the volitional approach emerged later and should not be confused with the suddenness objection. In United States v. Lyons the Fifth Circuit abandoned the control prong because current knowledge cannot reliably separate an impulse that was irresistible from one that was merely not resisted.²⁷ That objection concerns the difficulty of proof, whereas the Durham objection concerns the scope of the test: it complains that a test aimed at sudden loss of will overlooks illnesses that work slowly.