Criticisms of the Product Test

The product test did not reach its working form in the opinion that announced it. In the decade after Durham, the United States Court of Appeals for the District of Columbia decided more than a hundred appellate opinions on the sanity issue, a record of a court repairing a rule that had been announced in very few words.¹ Many of the criticisms had substance, so the court set about answering them by giving the test more content, and by the time that work was done the rule had begun to resemble the Model Penal Code test that eventually supplanted it.² The test is now generally described as an experiment that failed.³

Three objections, each aimed at a different part of the rule, account for most of that repair work and for the retreat from the test elsewhere. One concerns vocabulary, because neither product nor mental disease or defect arrived with a definition. A second concerns proof, because the causal question the rule asks is far easier to answer for one side than for the other. A third concerns the filter itself, because causation alone may excuse people the law has good reason to hold responsible. Each objection rests on its own mechanism and drew its own response, so the parts below take them one at a time.

Vagueness of Product

The first objection is that the original opinion left both of its operative phrases undefined. Durham made no effort to explain what product means, and it defined mental disease and mental defect only in relation to each other: a disease is a condition capable of improving or deteriorating, and a defect is a condition that is not.⁴ Critics therefore raised what can be called the vagueness objection, namely that the ambiguity left juries with insufficient guidance on the critical issue of responsibility.⁵ The same complaint had been made against the New Hampshire product rule, and experience in that state never produced the evidence needed to test it.⁶

The vagueness mattered more here than under the earlier tests, and the reason lies in what each test required the jury to find. Under the right-wrong test, the phrase disease of the mind did little work, because the jury's attention went to a specific effect, an inability to distinguish right from wrong. Under the product test the disease did not have to produce any particular effect. It only had to be a factor causing the crime, so what counted as a disease decided who qualified for the defense.⁷ A jury given no yardstick for either word has one place left to turn, which is the psychiatric witness. The jury was left dependent on the expert's classification of the conduct as the product of mental disease, and the courtroom dispute shifted from the words of the rule to the nature of the particular disease.⁸

The dependence on labels had visible consequences. In 1957 a staff conference at St. Elizabeth's Hospital in Washington reclassified psychopathic personality as a mental disease, and because that single hospital supplied most of the psychiatric witnesses in the District's courts, juries were abruptly told that certain defendants who had previously been considered responsible were now to be acquitted.⁹ In Blocker v. United States the court ordered a new trial for a defendant with a sociopathic personality when, after his conviction, the psychiatric profession, or part of it, changed its view and began calling sociopathy a mental disease.¹⁰ In both episodes the legal outcome moved with a medical label while the facts about the defendant stayed where they were, and a test that lets every case stand or fall on the testifying psychiatrists' classifications leaves the court little room for an independent legal and social judgment.¹¹

The District of Columbia court answered in installments. Carter v. United States supplied the meaning of product, requiring that the facts permit a reasonable inference that the accused would not have committed the act without the disease.¹² McDonald v. United States addressed the disease half. The court recognized the injustice of resting a defense on a temporary psychiatric classification, and it observed that calling a condition a disease for psychiatric purposes is not necessarily accurate for purposes of the criminal law, so it redefined mental disease or defect to include "any abnormal condition of the mind which substantially affects mental or emotional processes and substantially impairs behavior controls."¹³ That definition gives jurors something to measure against the evidence of how the defendant actually functioned, whichever label the experts prefer. The court eventually concluded that the standard had to describe the kinds of effects of disease that matter to compliance with the criminal law, and in 1972 it overruled Durham in favor of a modified Model Penal Code test.¹⁴

The two charges differ in one respect, which is whether the instruction tells the jury what the disease must do. Students lose this point when they describe the product test as undefined without noting the later definitions of product and mental disease, since the vagueness criticism targets the original opinion and the court answered it over the following years.¹⁵ The second objection does not depend on vocabulary at all, because it holds that even a well-defined product question is hard to prove.

The Needle-in-Haystack Problem

The second objection concerns what the but-for definition demands of proof. Carter defined product to mean that the facts about the disease and the facts about the act justify a reasonable inference that the accused would not have committed the act if he had not been diseased as he was.¹⁷ That question asks a witness to say what a particular person would have done with a different mind, and critics objected that it demands a mental gymnastic no one can perform with confidence, since nobody can observe the same person minus the illness.¹⁸ Others added that the causal problems closely resembled those that had troubled the right-wrong and irresistible impulse tests the product test was meant to replace.¹⁹

The difficulty is lopsided, and the lopsidedness is what turns a theoretical worry into a problem of proof. A psychiatrist can sometimes point to evidence that links a disease to an act, such as the content of a delusion that names the victim. To say that an act was not a product of the illness, the same psychiatrist would have to exclude every way the illness might have shaped the conduct, and that exclusion can rarely be made with confidence. The image critics used is a needle in a haystack: a searcher may sometimes find the needle but can never demonstrate that none is there. A firm expert opinion on the product question would therefore almost invariably favor the defendant, and this proof imbalance is the second objection in its simplest form.²⁰

The imbalance bites because of who carried the burden. Under the instruction Durham suggested, the jury could convict only if it believed beyond a reasonable doubt either that the accused was not suffering from a diseased or defective mental condition or that the act was not the product of one.²¹ The prosecution therefore had to establish a negative to the highest standard of proof, through witnesses who could seldom supply it. Critics described that as an impossible position for the prosecution, and the cases decided under Durham bore out the criticism.²²

The court's response left the but-for definition in place and changed who could announce the answer. In Washington v. United States, decided in 1967, it held that psychiatrists could no longer testify whether the alleged offense was the product of mental illness, and that holding largely overcame the imbalance.²³ The remedy fits the problem because the asymmetry lived in the expert's conclusion, where only the affirmative answer could realistically be given with confidence. Once no expert may announce a conclusion on product, each side's witnesses describe the defendant's condition and the jury draws the causal inference from the whole record, which removes the one-way pull of conclusory testimony.

The two witnesses in the example differ only in the direction of the question they are asked. Students lose this issue when they read the criticism as a charge that psychiatrists favor defendants, since the problem is the logic of proving a negative and applies to an honest expert on either side.²⁴

Overbreadth Concern

The third objection accepts that the causal question can be asked and challenges whether answering it is enough. Its proponents argued that, even if a criminal act can be the product of a mental disease, that fact should not by itself excuse the defendant. In their view the defense should apply only when the condition affected the defendant so substantially that he could not appreciate the nature of the illegal act or could not control his conduct.²⁶ A member of the District of Columbia court voiced this overbreadth objection from within, and others made a related argument that a responsibility test should be drawn narrowly enough to exempt from punishment only people who cannot be deterred.²⁷

The objection makes sense against the reason an illness excuses at all. Durham started from the premise that the mind functions as a unit, so that a person with a mental disease could not be expected to respond properly to threats of sanction and was not a fit object of anger and blame.²⁸ If that premise held in every case, a causal link between illness and act would itself show an inability to respond. The critics denied that the link shows this. A condition can shape a person's motives, for example by making the person quick to anger, without removing the ability to understand that an act is wrong or to stop. Someone in that position still responds to the threat of punishment, so excusing the person removes the deterrent exactly where it can work and extends the defense to people the law has reason to hold responsible.

This objection mirrors the complaint that produced the product test. The Durham court rejected the earlier tests because one rested on a single symptom and the other gave no recognition to illness marked by brooding and reflection, so both excluded mentally ill defendants whose condition showed itself differently.²⁹ The product test removed the symptom requirement entirely, and with it any requirement that the illness have impaired the capacities the law cares about. The earlier tests risked excusing too few defendants, and the critics said the new one risked excusing too many.

The court did not abandon the but-for definition of product. It answered the overbreadth objection indirectly, by tightening the definition of mental disease and defect.³⁰ Under the McDonald definition, only an abnormal condition that substantially affects mental or emotional processes and substantially impairs behavior controls qualifies.³¹ The phrase about behavior controls does the filtering: a condition that causes an act while leaving behavior controls intact falls outside the definition, so the causal question is put only for conditions that already affect capacity. The Model Penal Code later made the filter explicit, excusing a person only if, as a result of mental disease or defect, the person lacks substantial capacity either to appreciate the wrongfulness of the conduct or to conform it to the requirements of law.³²

Hypothetical Illustration

A defendant with a diagnosed mood disorder becomes irritable under stress. After a coworker makes a joke at the defendant's expense, the defendant punches the coworker. The evidence supports an inference that, without the disorder, the defendant would have laughed it off. She understood that punching a coworker was wrong and she could have walked away. Under a test that asks only whether the act was a product of the disease, the jury may find the punch a product and acquit. Under the later definition, the jury must also find that the condition substantially impaired behavior controls, and the evidence that she could have walked away points against that finding. Change one fact, so that the disorder left the defendant unable to stop once agitation began, and the condition meets the definition, which makes the causal inquiry the deciding question.

The pair of situations differs in a single variable, which is whether the illness reached the defendant's capacity to control the act. Students lose this issue when they assume that a causal link between the illness and the act shows the accused lacked capacity, since an illness can cause an act without removing the ability to appreciate or control it.³³ Each of the three responses moved the product test closer to a capacity-based test, and the next section follows that movement to its end.

Vagueness of Product

The first objection to the product test goes to the words the court chose. In Durham v. United States the court held that an accused is not criminally responsible if his unlawful act was the product of mental disease or defect, yet it made no effort to explain what "product" meant in that setting and did not define mental disease or mental defect.³⁵ The opinion drew a single distinction, between the two nouns: a disease is a condition capable of improving or deteriorating, and a defect is not.³⁶ That distinction told a juror nothing about which conditions qualified or how closely a condition had to be tied to the act, and the ambiguity in both phrases became the standard criticism of the rule as originally formulated, the vagueness objection.³⁷

A missing definition matters because a jury instruction exists to hand jurors a question they can answer by measuring the evidence against a standard. When the controlling word is undefined, the question stays open, and each juror fills it with a private view of what causation or illness requires. Critics therefore called the rule a nonrule: it supplied no standard for judging the evidence and did not direct the jury to the pathological factors the law cares about, the impairment of reason and control, so jurors depended entirely on an expert's classification of the conduct as the product of disease.³⁸ The court had assumed that the concept of mental disease would give expert testimony a better framework than the earlier tests, and it left the term almost undefined so that the courtroom contest would move from the wording of the rule to the nature of the particular disease.³⁹ The same weakness appears in trial practice, because parties cannot predict how an undefined question will be decided and cannot argue it with confidence.

The second phrase, mental disease or defect, created its own difficulty because of the role it played in the test. Under the right-wrong test the disease of the mind had to produce a discernible effect, an inability to tell right from wrong, so courts rarely cared what counted as a disease. Under the product test the disease did not have to be anything except a factor causing the crime, which made the label carry the entire weight of the filter.⁴⁰ A label with no definition behind it moves whenever professional opinion moves. In 1957 a staff conference at St. Elizabeth's Hospital in Washington reclassified psychopathic personality as a mental disease, and because that hospital supplied most of the psychiatric witnesses in the District's courts, juries were abruptly told that certain defendants once considered responsible were now to be acquitted.⁴¹ Nothing about those defendants had changed, only the label, and a test that lets every case stand or fall on the classifications psychiatrists use leaves the court little room for an independent legal and social judgment.⁴²

The drafters of the Model Penal Code treated this ambiguity as reason enough to reject the product test.⁴³ Their provision excuses a person who, as a result of mental disease or defect, lacks substantial capacity either to appreciate the wrongfulness of the conduct or to conform it to the requirements of law.⁴⁴ The Code still contains a causal phrase, but it ties that phrase to a defined effect. Instead of asking whether the crime was the product of a disease, it asks what impact the disease had on the person's cognitive or behavioral capacities, which gives jurors a concrete question about how the defendant actually functioned.⁴⁵

The District of Columbia court tried to answer the objection from inside the product framework. Carter v. United States defined product to require but-for causation, so that but for the mental disease or defect the accused would not have committed the crime.⁴⁶ By 1962 the court also required trial judges to tell juries that mental disease or defect includes any abnormal condition of the mind that substantially affects mental or emotional processes and substantially impairs behavior controls.⁴⁷ With those definitions in place the Durham rule began to resemble the Model Penal Code test, and in 1972 the court abandoned Durham in United States v. Brawner, decrying the "trial by label" that had resulted.⁴⁸

The objection is aimed at the rule as originally formulated, so a statement that the product test is hopelessly undefined overlooks the definitions the court added over the following years.⁴⁹ Those definitions did not end the criticism, however. Some critics said the but-for question demands a mental gymnastic, since no one can say what a person would have done with a different mind.⁵⁰ Clarifying the word gave jurors a question to answer, but it left open how that question could be proved and whether causation alone is the right filter, and the next two objections take up those problems in turn.

The Needle-in-Haystack Problem

The vagueness objection concerned the words of the test. The second objection concerns proof, and it survives even after the words are defined. When Carter v. United States defined product in 1957, jurors received a question they could state: the facts about the disease and the facts about the act had to justify the conclusion that, but for the disease, the act would not have been committed.⁵² A question can be perfectly clear and still be one that only one side can answer with confidence. Critics said this was such a question, because it demanded an answer that could seldom be given.⁵³ Their complaint is called the proof imbalance objection, and it has to be separated from a neighboring complaint before its logic is visible.

The neighboring complaint is that the but-for inquiry is a mental gymnastic, since no one can say what a person would have done with a different mind.⁵⁴ That difficulty bears on both sides alike. The imbalance objection adds that the difficulty falls unevenly, because only one of the two possible answers has evidence to rest on. An affirmative answer can be assembled from facts that exist in the real world: a diagnosed condition, the symptoms that characterize it, and a close fit between those symptoms and the act. A negative answer has no comparable material, because it must exclude every route by which the illness might have contributed to the act. The premise behind Durham was that mental disease may impair the whole mind and not merely one compartment of it, which makes the negative answer harder still, since a psychiatrist who has diagnosed such an illness is poorly placed to certify that a particular act lay outside its reach.⁵⁵ The critics' summary was that an expert can occasionally say an act was a product of mental disease but can rarely, if ever, say it was not.⁵⁶ A searcher may sometimes find a needle in a haystack, yet no search can establish that the hay holds no needle at all, and the court's own decisions under Durham reflected that lopsidedness.⁵⁷

The imbalance matters because a rule whose outcome turns on a question that one side can answer and the other cannot hands an advantage to the first side regardless of the merits. If experts could affirm causation but not deny it, a firm opinion on the product issue would almost invariably favor the defendant, and the prosecution would have no witness able to supply the matching answer.⁵⁸ The unfairness does not depend on anyone testifying dishonestly. An honest prosecution expert who doubts that the illness explains the act can usually say only that causation is unproven, and that qualified statement sounds weak beside a confident affirmative from the defense.

The District of Columbia court answered the problem in Washington v. United States in 1967 by limiting psychiatric testimony to a description of the defendant's mental condition, leaving the jury to decide whether the condition was a mental disease or defect and whether the crime was a product of it.⁵⁹ Psychiatrists could therefore no longer testify whether the alleged offense was the product of mental illness, and that holding largely overcame the imbalance.⁶⁰ The remedy fits the problem because the asymmetry lived in the expert's conclusion, where only the affirmative could realistically be given with confidence. Once no witness may announce a conclusion on product, both sides' experts describe the illness and the act, and the jury draws the causal inference from the whole record.

Students lose this issue when they read the later holding as a ban on psychiatric evidence, since it removed only the expert's conclusion on product and left the expert free to describe the disease and its effects. The causal question itself stays in the case and goes to the jury. The but-for definition therefore remained in place, and a third objection accepted that the causal question could be asked and answered but challenged whether causation alone should excuse a defendant at all.

Overbreadth Concern

The third objection takes for granted that jurors can understand the word product and that the evidence can answer the but-for question, and it still says the formula reaches too far. The formula excuses any accused whose unlawful act was the product of mental disease or defect, and the product test has been criticized as too broad because it sweeps in people whom the law has no reason to excuse.⁶² This overbreadth objection was voiced from within the District of Columbia court itself, and it locates the flaw in causation as the filter: even assuming that a criminal act can be the product of a mental disease, "that fact should not per se excuse the defendant."⁶³ On this view the defense should succeed only when the condition affected the accused so substantially that he could not appreciate the nature of the illegal act or could not control his conduct.⁶⁴

The objection has force because of what criminal punishment is for. A sanction works partly by deterrence, since the threat of punishment gives a person a reason to refrain, and partly by blame, since conviction condemns someone who chose wrongly. Both functions assume that the person could grasp what the act was and steer his conduct accordingly. For that reason the critics said a test of responsibility should be drawn narrowly enough to exclude from punishment only the nondeterrables, meaning those whom the threat of a sanction cannot reach because the illness leaves them unable to appreciate or control what they do.⁶⁵ Causation does not sort people along that line. A condition can be a but-for cause of an act in ways that leave understanding and self-control largely intact, for example by sharpening a mood that the person could still have governed, and such a person remains someone the threat of punishment can reach. The original product test made this mismatch likely, because it started from the premise that the mind is a functional unit and reasoned that anyone with a mental disease could not be expected to respond properly to threats of sanction.⁶⁶ When that premise fails on the facts of a particular case, a rule that asks only about disease and product excuses anyway.

The disease element might have screened out cases like this one, but under the original rule it did very little filtering. The mental disease or defect did not have to be anything in particular except a factor causing the crime, which is why the choice of label mattered so much.⁶⁷ In Blocker v. United States the court held that a defendant with a sociopathic personality was entitled to a new trial after the psychiatric profession, or a portion of it, changed its view and began calling sociopathy a mental disease.⁶⁸ A causal requirement combined with an elastic disease category meant that each widening of the psychiatric vocabulary widened the class of excused defendants, with no independent legal check on how impaired a defendant had to be.

The District of Columbia court did not rewrite the product element to meet this objection. It kept the but-for definition of product, and the criticism was overcome indirectly by its later action in defining mental disease or defect.⁶⁹ In 1962, in McDonald v. United States, the court observed that mental disease means one thing to a physician bent on treatment and something different, if overlapping, to a court of law, and it supplied a legal definition: any abnormal condition of the mind which substantially affects mental or emotional processes and substantially impairs behavior controls.⁷⁰ The footnotes to United States v. Brawner record the same definition as McDonald's attempt to clarify the Durham rule.⁷¹ The definition moves the filter the objection wanted into the first element. Before a jury reaches the question of product, the condition itself must substantially affect mental or emotional processes and substantially impair behavior controls, so a disorder that only colors a person's mood no longer qualifies and the causal question never arises. The answer is still indirect, because the definition speaks of substantial impairment rather than of inability and leaves the product requirement standing, yet it carried the Durham rule toward the capacity-based test that later supplanted it.⁷²

This objection is easy to confuse with the two before it, and the confusion costs points. The vagueness objection says jurors lack a standard, and the proof imbalance objection says the causal question cannot fairly be answered. The overbreadth objection grants that the causal link exists and denies that the link is enough. Its remedy is therefore a second requirement, substantial impairment of the capacity to appreciate or control, which is the same pair of capacities the Model Penal Code later made the express standard.⁷³