The cognitive psychology of mens rea.

• Author: Heller, Kevin Jon

1. INTRODUCTION

   Actus non facit reum nisi mens sit rea--"the act does not make a person guilty unless the mind is also guilty." (1) Few today would disagree with the maxim; the criminal law has long since rejected the idea that causing harm should be criminal regardless of the defendant's subjective culpability. (2) Still, the maxim begs a critical question: can jurors accurately determine whether the defendant acted with the requisite "guilty mind"? St. Thomas Aquinas was certainly skeptical that such mindreading--as cognitive psychologists call it (3)--is within the ken of mere mortals:

   [M]an, the framer of human law, is able to judge only of outward acts; because man seeth those things that appear, according to 1 Kings 16.7; but God alone, the framer of the Divine law, is able to judge the inward movement of wills.... (4) Given the significant cognitive demands contemporary criminal law imposes on jurors, Aquinas's skepticism seems more prescient than ever. The common law, for example, not only asks jurors to distinguish between seventy-eight different terms for mental states, (5) it fails to define the various mental states consistently--there are seven different definitions of willful alone (6)--and combines them in permutations that defy comprehension. (7) Indeed, the common law is such a mess that no less an authority than Justice Robert Jackson once bemoaned the "variety, disparity, and confusion" of the "requisite but elusive mental element." (8)

   The Model Penal Code (MPC), adopted by a majority of states, (9) may actually be worse. To be sure, the MPC takes a far more systematic approach to mens rea, winnowing the common law's seventy-eight mental states to four: purpose, knowledge, recklessness, and negligence. (10) Those mental states are differentiated with such "subtlety and precision," however, that it is an open question whether jurors can accurately distinguish them. (11) Consider, for example, the MPC's three subjective mental states: a person acts "purposely" if his "conscious object" is to bring about a particular result; (12) acts "knowingly" if he is "aware that it is practically certain" that his conduct will lead to the result; (13) and acts "recklessly" if he "consciously disregards a substantial and unjustifiable risk" that his conduct will cause the result. (14) Those are fine distinctions, to say the least. Little wonder, then, that scholars have described the MPC as an "elaborate set of precise rules whose operability depends on the jury's willingness"--to say nothing of their ability--"to make artificial characterizations." (15)

   The MPC's idiosyncratic definition of negligence only further complicates mindreading. Negligence is defined as the defendant acting "when he should be aware of a substantial and unjustifiable risk" that his conduct will lead to a particular result. (16) Common law negligence is not actually a mental state; the reasonable-person standard "is determined and applied without reference to what the actor was thinking at the moment." (17) The MPC, by contrast, subjectivizes negligence, once again requiring jurors to read the defendant's mind: whether the defendant's conduct was unreasonable must be determined "considering the nature and purpose of his conduct and the circumstances known to him" at the time of the crime. (18)

   Nor is that all. Although the common law at least limited each offense to a single mental state, (19) the MPC permits different mental states to apply to different material elements of an offense--what is known as "element analysis." (20) Misdemeanor indecent exposure is an example: "A person commits a misdemeanor if, for the purpose of arousing or gratifying sexual desire ... he exposes his genitals under circumstances in which he knows his conduct is likely to cause affront or alarm." (21) Thus defined, a jury must determine both whether the defendant acted knowingly (with regard to his conduct's potential to cause affront or alarm) and whether he acted purposely (with regard to arousing or gratifying sexual desire)--a far more complicated mindreading task than determining a single mental state.

   This discussion also assumes that jurors normally determine whether the defendant is guilty of a single crime. In many cases, of course, jurors will have to choose between multiple closely-related crimes, whether because the prosecution has charged them in the alternative or because they are added in jury instructions as lesser-included offenses. Jurors in a homicide case, for example, may be asked to determine whether the defendant is guilty of first-degree murder, second-degree murder, reckless homicide, or criminally negligent homicide. Those charges are normally distinguished solely by the mental state they require: a "premeditated and intentional" killing for first-degree murder; (22) a "knowing" killing for second-degree murder; (23) a "reckless" killing for reckless homicide; (24) and "criminally negligent conduct" that results in death for criminally negligent homicide. (25)

   Finally, in most criminal cases, jurors will have to deal with yet another mental state: namely, the one associated with the defense the defendant uses to negate the mens rea of the charged crime. (26) A defendant may defend himself against a murder charge, for example, by alleging that he was legally insane at the time of the killing. (27) Most often, as in the murder example, the focus will be on the defendant's lack of a "guilty mind." In some cases, however, the defendant may invoke a defense that shifts attention to the victim's mental state at the time of the crime--a rape case, for example, in which the defendant claims that the victim consented to the sex.

   It is fair to say, in short, that contemporary criminal law requires jurors to be latter-day Kreskins--to not only reliably distinguish nearly-indistinguishable mental states, but also to accurately determine which of many possible mental states the defendant actually possessed at the time of the crime. (28) Is such mindreading possible? Or is Aquinas correct that "God alone ... is able to judge the inward movement of wills"?

   Given the centrality of mens rea to criminal responsibility, we would expect legal scholars to have provided a persuasive answer to this question. Unfortunately, nothing could be further from the truth. Most scholars simply presume that jurors can mindread accurately, and those that take mindreading seriously have uniformly adopted "common sense functionalism," (29) a theory of mental-state attribution that is contradicted by a vast amount of research into the cognitive psychology of mindreading. Common-sense functionalism assumes that a juror can accurately determine a defendant's mental state through common-sense generalizations about how external circumstances, mental states, and physical behavior are causally related. (30) Research indicates, however, that mindreading is actually a simulation-based, not theory-based, process. When a juror perceives the defendant to be similar to himself, he will mindread through "projection," attributing to the defendant the mental state that he would have had in the defendant's situation. And when the juror perceives the defendant to be dissimilar to himself, he will mindread through "prototyping," inferring the defendant's mental state from the degree of correspondence between the defendant's act and his pre-existing conception of what the "typical" crime or defense of that type looks like.

   The goal of this Article is to provide a comprehensive--though admittedly speculative--explanation of how jurors use projection and prototyping to make mental-state attributions in criminal cases. The Article is divided into six Parts. The first two provide the necessary background: Part II sketches the traditional functionalist explanation of mindreading, and Part III explains why jurors are unlikely to use a functionalist method in a case that focuses on the defendant's mens rea. The next two Parts are descriptive: Part IV introduces projection and prototyping and discusses the evidence that jurors use them to make mental-state determinations, while Part V explains the cognitive mechanism--perceived similarity between juror and defendant--that determines which technique a juror will use in a particular case. The final two Parts are then analytic: Part VI explains why projection and prototyping are likely to result in inaccurate mental-state determinations, and Part VII discusses de-biasing techniques that could be used to improve their accuracy.

2. THE TRADITIONAL EXPLANATION

   Rebecca Dresser has argued that "the general legal reaction to the proof issues raised by other minds judgments is either to ignore or to dismiss them." (31) It is difficult to disagree. Aside from Dresser's own article and an article by Adam Candeub, (32) one searches the legal literature in vain for a sustained discussion of the psychology of juror mindreading. Most scholars, it appears, simply presume that accurate mindreading is possible--a position that dates back at least to 1882, when Bowen famously dismissed Oliver Wendell Holmes's skepticism toward mindreading (33) by claiming that "the state of a man's mind is as much a fact as the state of his digestion." (34) Little has changed in the intervening century. In fact, as recently as 1987, Richard Singer could assert without argument that "[i]t is certainly within the jury's ken to find that a typical self defender did not intend (purpose) a killing." (35)

   The question, of course, is why legal scholars take it for granted that jurors can make accurate mental-state determinations. As discussed above, (36) given the significant cognitive demands that contemporary criminal law imposes on jurors, it is far from obvious that they can. The answer seems to be that legal scholars embrace, implicitly or explicitly, a commonsense theory of mental-state attribution in which mindreading seems neither particularly complicated nor...