The Psychological Foundations of Evidence Law

Michael J Saks, Barbara A Spellman

• Publisher: NYU Press
• Year: 2016
• ISBN:
  9780814783887
• Topic: Derecho
• Subtopic: Teoría y práctica del derecho

Evidence law is meant to facilitate trials that are fair, accurate, and efficient, and that encourage and protect important societal values and relationships. In pursuit of these often-conflicting goals, common law judges and modern drafting committees have had to perform as amateur applied psychologists. Their task has required them to employ what they think they know about the ability and motivations of witnesses to perceive, store, and retrieve information; about the effects of the litigation process on testimony and other evidence; and about our capacity to comprehend and evaluate evidence. These are the same phenomena that cognitive and social psychologists systematically study. The rules of evidence have evolved to restrain lawyers from using the most robust weapons of influence, and to direct judges to exclude certain categories of information, limit it, or instruct juries on how to think about it. Evidence law regulates the form of questions lawyers may ask, filters expert testimony, requires witnesses to take oaths, and aims to give lawyers and factfinders the tools they need to assess witnesses’ reliability. But without a thorough grounding in psychology, is the “common sense” of the rulemakers as they create these rules always, or even usually, correct? And when it is not, how can the rules be fixed? Addressed to those in both law and psychology, The Psychological Foundations of Evidence Law draws on the best current psychological research-based knowledge to identify and evaluate the choices implicit in the rules of evidence, and to suggest alternatives that psychology reveals as better for accomplishing the law’s goals.

Part I

Minding the Jury

1

Judges versus Juries

Trying the Facts

To get a sense of what a typical American juror’s experience is like, imagine taking a college course in which there is no textbook or other background reading. Where most of the information you need to learn is delivered orally, by different lecturers, whose facts and perspectives often conflict. Where you are not permitted to take notes or ask questions, and not allowed to discuss the unfolding information with anyone, including the people with whom you will have to work collaboratively on the “final exam.”1

No doubt you are beginning to appreciate that jurors have a challenging job. They must draw conclusions from evidence that often is scanty, missing, conflicting, and only semi-organized. They must attempt to reconstruct the facts of a disputed transaction and draw inferences not only about observables but also about unobservable occurrences (e.g., intentions, knowledge, and other mental states). Traditionally, and still typically, the jury is required to listen passively to evidence (direct and cross-examination), arguments, and instructions, view exhibits, and then try to sort it all out—without taking notes, without reviewing relevant evidence presented yesterday or last week, and without asking questions or discussing the evidence with the witnesses or (until the close of evidence) with each other.

Occasionally during the trial the judge will instruct the jurors to perform feats of mental virtuosity (e.g., to use a piece of evidence for one purpose but not another). And to make it even more difficult, most of what the jury will learn about the law and the ultimate decision-making task that it has been recruited to perform will be deferred until the end of the trial, delivered by the judge in one final lecture, likely to be given in language that is at best stilted and at worst opaque. Each juror’s goal, by the end of the trial, is to take the messy and disputed facts learned during the trial and create a more or less coherent narrative for his or her own use; infer necessary mental states and relationships (e.g., causation); figure out what the applicable law wants done with those facts; debate their thoughts with the other jury members; reach a collective verdict; and, in appropriate cases, award damages or impose punishment.

Judges apply the rules of evidence to regulate what the jury can hear, how they may hear it, and how they may use what they hear. In general, the rules are designed to increase the likelihood that the jurors’ efforts will produce a correct and proper outcome. (See Rule 102.) But the rules express other values in addition to getting to the right decision—such as efficiency, public policy (e.g., encouraging settlements and plea agreements), protecting the privacy of victims (e.g., in rape trials), and safeguarding the confidentiality of some relationships (e.g., spouses; lawyers and clients). The various rules guarding these other values sometimes make the jurors’ job even more difficult.

Rule 102. Purpose

These rules should be construed so as to administer every proceeding fairly, eliminate unjustifiable expense and delay, and promote the development of evidence law, to the end of ascertaining the truth and securing a just determination.

The jury’s task, the judge’s management of it, and the part played by the rules of evidence raise numerous questions. Why does the law think rules of evidence are needed? How do the rules of evidence affect the relationship between the judge and jury and the role each plays in trials? How important is evidence, as compared to other factors—such as the backgrounds, beliefs, and biases of the people who make up the jury? How do individual jurors, and the jury as a group, make decisions using evidence? How (and why) do the decisions of juries differ from those of judges?

Division of Labor: How the Roles of Judge and Jury Interact

Having both a judge and a jury at trials allows for a division of labor: the judge is the “trier of law” and the jury is the “trier of fact” or “factfinder.” When there is a jury, the judge can screen evidence in ways that would not be possible for a judge sitting alone. Although in principle the rules of evidence apply regardless of whether the factfinder in a case is a judge or a jury, the practical reality is that the rules cannot be applied well in a bench trial (that is, when the presiding judge is also the factfinder). Applying the rules requires that someone (the judge) first decide whether evidence that is objected to ought to be admitted, limited in some way, or excluded altogether, and then someone else (the jury) can work their way to a verdict based only on that admitted evidence. The judge cannot do both, because in performing the first task the judge is learning the sometimes toxic facts that are supposed to be excluded from consideration. (That is, the judge is suffering from a type of mental contamination, discussed in the Introduction.) Although judges and legal theorists have long thought that judges can hear the excludable evidence and then “give it appropriate weight” (including zero weight when the rules require exclusion), empirical studies, as we shall see below, have not borne out that expectation. The jury, on the other hand, gets to focus exclusively on evidence that has passed through the judicial filter.

However, judges sitting with juries do have some judicial factual determinations to make in the course of deciding what evidence to admit and what to exclude.2 Some examples are rulings on motions asking that evidence be suppressed as being in violation of the Fourth Amendment’s prohibition on unreasonable search and seizure, or whether the circumstances exist that require the admission of what otherwise would be inadmissible hearsay, or whether scientific evidence achieves the degree of reliability required for it to be admissible as expert testimony. For all of these determinations, when the judge rules that exclusion is proper, the judge will be aware of the excluded evidence, but the jury will have been protected from learning it.

That said, “blindfolding” the jury to certain kinds of evidence is not always the best way to minimize the impact of inappropriate evidence.3 When evidence can be kept from the jury without the jury being aware of the exclusion, or without the jury wondering about that issue on its own with no prompting, blindfolding should do its job effectively. But some issues will come to jurors’ attention regardless of whether or not they are addressed by witnesses or the court. For example, in determining damages in a tort case, the jury will often wonder about insurance or whether to reduce damages for a plaintiff who was partly responsible for an accident. For such issues, it usually is better to explain the situation to the jurors and appeal to their duty and good sense to endeavor to reach their decision as the law has determined it should be made.4 In other situations, where the jury becomes aware that it has been deprived of evidence that it senses would be informative in reaching their verdict, they might place a higher value on the excluded evidence than it deserves. If the jury guesses incorrectly at the content of excluded evidence, and relies on its guess, the situation is made even worse.

What at first glance might seem to be inefficient and redundant use of multiple decision makers, could instead be an ingenious use of two different decision makers—judges and juries—in ways that obtain the best service of each, and who together enable trials to be more fair than they otherwise could be.

How Jurors and Juries Decide

In assessing the research on jury decision making, the bottom line is that despite many worries about many factors that might influence jurors in undesirable ways, the major factor affecting a jury’s decision seems to be the evidence presented at trial. The most important thing for lawyers and judges and rulemakers to worry about, therefore, is the evidence.

Jurors versus the Evidence They Receive

A common belief about trials is that the verdicts of juries are driven by “who they are”; that is, by the biases jurors bring with them to court. If that were so, an attorney who could shape the jury’s composition to consist of more favorable jurors would have the case nearly won before the opening statements were presented. However, a substantial body of empirical research has found that, for the great majority of cases, the characteristics of the jurors make only a modest difference to the verdict, whereas the evidence and arguments presented at trial have the greatest impact.5

The research that has produced these findings ranges from post-trial interviews with and surveys of jurors, to studies of jury-eligible citizens sometimes conducted by parties in preparation for jury selection in trials, to experiments using mock trials that systematically vary case facts. Each type of study, in its own way, examines the relation between the characteristics of the jurors and the decisions they make about key trial issues or their verdict preferences. Those juror characteristics have included beliefs about and attitudes toward numerous background issues (e.g., attitudes toward corporations) as well as trial-specific issues, personality attributes, and demographic characteristics (e.g., age, sex, education, political affiliation, income).

Predictive power is typically calculated by measuring how much of the variation in what is to be predicted (e.g., verdicts) can be accounted for by the predictors (e.g., juror attitudes, demographics). Even by combining the best predictors together, juror characteristics have been found on average to account for only 10–15% of the variation in verdicts.6 That leaves about 85–90% of the variance to be explained by other things, and those other things are largely the evidence and arguments presented in the case.7

Why would this be? Why would our impressions and intuitions about what leads people—our friends, our family, our co-workers, our classmates—to make the decisions they make not be reflected in these studies of juries? When we pause to consider the nature and circumstances of jury trials, the findings look far less surprising.

The process of assembling a jury includes eliminating those who have personal connections to, or too much familiarity with, any of the participants in the trial (“challenges for cause”). By insuring that jurors have no relationship with any of the trial participants, and therefore little probability of future interaction with those persons, the law eliminates some of the most powerful sources of influence. Typically, lawyers can also reject a number of prospective jurors whom they suspect have views contrary to the interests of their clients (“peremptory challenges”). To the extent that lawyers succeed in removing persons with the most extreme views, the jurors who remain are a more moderate mix (compared to whatever pool the selection began with). The selected jurors are then immersed in a social setting (the courtroom trial) that they have learned about from prior experience on juries or the wider culture (e.g., movies, books, news reports), which is reinforced by the judge’s specific admonitions. This particular social setting emphasizes norms of neutrality, fairness, and the duty to set aside bias and to focus on evidence. That is not what life outside the courtroom is like.

Moreover, the jury is a group. Jurors have to defend and justify their views to the other jurors in light of the evidence that has been presented at the trial. Engaging in these processes can cause jurors to change their own minds as well as other jurors’ minds.

But even studies of individual jurors, not just juries, suggest that the evidence carries the most weight, not the juror’s initial biases. That is, different jurors tend to reach the same decisions when presented with the same evidence and arguments about the evidence. In part, this occurs because the juror’s task is to solve the problem presented, to reach the correct answers based on the evidence at hand. In part, it is because many of the beliefs and biases relevant to deciding most cases are widely shared by members of a community. Thus, the research findings do not mean that people do not have attitudes and beliefs, or that their minds are blank slates before they come to the courtroom; rather, the findings suggest that people tend to have similar beliefs and biases about the issues they are assembled to resolve. Whether or not one believes in global climate change or evolution or Keynesian economics is of no relevance when deciding whether trial evidence supports the conclusion that the traffic light was red when the crash occurred or whether the defendant’s firing of the gun was done negligently or purposefully.

Though the above discussion applies to the great majority of cases, it does not extend to all cases, and there are some important exceptions to the generalization that jurors are largely interchangeable. Individual factors are most likely to matter if cases are close, if they involve non-common knowledge, or if personal attributes are an issue.

If the evidence is close, then juror characteristics and predispositions become more important to the trial’s outcome. When people make decisions, and a factor that would normally have a lot of influence (such as evidence) is, in effect, missing (because evidence is either lacking or is closely in balance), then weaker variables are more able to make themselves felt.8 In some kinds of cases the evidence is inherently close. For example, in cases of rape where the defense is consent, jurors often have little to go on other than the testimony of the defendant and the complaining witness—what he says versus what she says. In such cases, a set of beliefs referred to as rape myths are rather good at predicting how a juror will vote, and questions about those have been assembled into a questionnaire that (sometimes) can be asked of prospective jurors.9

If the evidence involves technical subjects, or requires more subtle reasoning, better-educated jurors tend to make more accurate decisions than jurors with less education, and jurors with specific training in the subject matter at issue will tend to make more accurate decisions than equally well educated jurors trained in other subject matters.10 In other words, and not surprisingly, those who understand medicine make better sense of medical evidence, whereas those who understand statistics make better sense of statistical evidence.

Still another exception to jurors being interchangeable is when personal attributes are made an issue in the case. The most familiar and most troubling example is when race or ethnicity becomes an issue: Did the police go after the defendant because of his race? Did the defendant attack the victim out of prejudice related to the victim’s nationality? A case that does not otherwise raise such issues can be turned into a racially divisive case by counsel—sometimes referred to as “playing the race card”—or by the news media. Jurors do not generally align into racial, ethnic, and other groupings. In a case involving police misconduct where race was heavily discussed by media, when reporters interviewed jurors afterward, the journalists were surprised to learn that the jurors had split not by race, but by age—older jurors trusted the police more than younger jurors did.11 But when circumstances render jurors’ own group identities salient by making those identities an i...

Table of contents

• Cover
• Title Page
• Copyright Page
• Dedication
• Contents
• Preface
• Acknowledgments
• Introduction: The Crossroads of Psychology and Evidence Law
• Part I. Minding the Jury
• Part II. Judging the Witness
• Part III. Other Types of Evidence
• Appendix A: Table of Concepts
• Appendix B: Federal Rules of Evidence (Abridged)
• Notes
• Index
• About the Authors