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Philosophy and Law Index The following appeared in Volume 96, Number 2 (Spring 1997) of the APA Newsletters.
EVIDENCE, PERSUASION, AND THE JURY
Michael J. Saks
College of Law
University of Iowa
Perhaps surprisingly, given popular perceptions, the presentation of evidence and arguments is where most of the action is in trials. Studies that have pitted trial evidence and arguments against what jurors bring with them to court usually find that the trial information carries much more weight.1
Indeed, every researcher who does mock jury experiments is acutely aware that the case facts need to be pre-tested and adjusted lest they swamp the (usually more subtle) variables that are the focus of the study.2 In order to maximize the possibility of detecting the effects of the variables under study, researchers usually aim to produce cases that are ambiguous, that bring jurors near the midpoint of the scale of voting preferences. This insight from the experimenter’s craft bespeaks a widely held, if sometimes unacknowledged, awareness of the power of case information.
This fact, in turn, suggests that everything that social psychologists, communications researchers, and others know about the phenomena of belief and attitude formation and change becomes relevant to understanding how the information that is presented at trials leads jurors to the decisions they reach. While a detailed review of that literature is beyond the scope of this note, the literature exists for the interested scholar or litigator to consult.3
Demeanor: Non-verbal Communication
Trial courts put enormous stock in assessment of the credibility of witnesses as a vital path to correct factfinding. Moreover, they have remarkable faith in the ability of factfinders to evaluate credibility by using demeanor evidence. Appellate courts routinely defer to trial court factfinding based in part on the notion that the factfinders at trial were in a far superior position to judge the credibility of the evidence. Consider Learned Hand on the point:
The words used are by no means all that we rely on in making up our minds about the truth of a question that arises in our ordinary affairs, and it is abundantly settled that a jury is as little confined to them as we are. They may, and indeed they should, take into consideration the whole nexus of sense impressions which they get from a witness. This we have again and again declared, and have rested our affirmance of findings of fact of a judge, or of a jury, on the hypothesis that this part of the evidence may have turned the scale. Moreover, such evidence may satisfy the tribunal, not only that the witness’ testimony is not true, but that the truth is the opposite of his story.4
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How good are we humans at using demeanor evidence to detect truth-telling or lying? A considerable amount of research has been conducted in recent decades on non-verbal behavior and the detection of deception. The findings indicate that demeanor cues often reduce accuracy in detecting deception, by distracting people into looking at cues they think are associated with lying and overlooking cues that actually are. Table 1 summarizes the findings of a meta-analysis of a number of experiments.5 Observers receiving no information at all would have standard deviation scores of 0.00 (sheer guesswork). Where no speech is provided, but only non-verbal cues, observers do no better when they see the face and nothing else (0.05), noticeably better when they can see the body and not the face (0.43), and when they can see both together, their performance falls a bit (0.35). Apparently, facial cues provide little help and sometimes do more harm than good. By contrast, subjects given transcripts alone are better at detecting deception than any of the conditions we have considered thus far (0.70). Speech sounds alone, with no visual cues at all, raise performance further (1.09). So much for the notion that non-verbal channels of communication carry more information than verbal channels, for human deception detectors to rely upon. Adding body cues to speech raises performance to its height (1.49). Adding facial cues to speech-with or without body cues-drags performance below what it was with speech alone.
In sum, jurors would be better advised to disregard witnesses’s faces if they want to maximize their ability to detect deception, or just wear a blindfold and listen closely. Appellate judges listening to an audiotape would do at least as well (1.09) as jurors (or, presumably, trial judges) who had access to both face and body cues (1.00).
Central v. Peripheral Routes to Persuasion
Cacioppo & Petty6 have shown that many, perhaps most, attitude change phenomena involving communication of information can be explained by what they have termed the likelihood-elaboration model. This model is an outgrowth of earlier work on cognitive response analysis in persuasion research.7 This theory captures a multitude of research findings that suggest that attitude change is largely self-generated and results from a person’s cognitive responses to information.
If an argument is close to one’s own current position, a person tends to generate pro-arguments, and as a result the person moves (himself or herself) in the direction of the persuasive message. If an argument is quite far from a person’s own position, the cognitive response is to generate counter-arguments, which result in movement further away from the persuasion attempt. (Which thus explains the experimental findings of boomerang effects due to persuasion attempts that are too extreme.) If the persuasion attempt occurs in the presence of distractions, it has been found that a high level of distraction prevents attitude change but low to moderate levels of distraction actually increase the effectiveness of the persuasion attempt.8 A cognitive response analysis of these phenomena would be that distraction that is sufficient only to interfere with counter-arguing will enhance the effectiveness of the persuasive communication; distraction that interferes with message reception will, obviously, prevent any response to the message.
A person’s cognitive responses depend upon other variables. For example, the more informed the audience is or the more relevant the arguments are, the more ability they will have to counterargue and the more intensely they will scrutinize the content of the persuasive message. The less informed the audience or the less relevant the issue, the less cognitive processing of the message content and the more impact extraneous cues will have on attitude change. This has led Cacioppo and Petty to theorize two routes to persuasion: central and peripheral.
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The effects and implications of the two routes are illustrated by an experiment in which the researchers varied (a) the relevance of the issue (a message about senior comprehensive examinations that would go into effect either next year or ten years hence), (b) whether the source of the message was an expert on the topic or not, and (c) whether the message contained strong or weak arguments.9 The findings are given in Figure 1. Note that where the relevance of the message was low, the audience’s resulting attitudes were greatly affected by the status of the source (expert vs. nonexpert) and were not much affected by the strength or weakness of the arguments. This shows persuasion by the peripheral route (little focus on or response to argument content, great influence of superficial cues). Where the relevance of the message was high, the audience’s resulting attitudes were little affected by the status of the source but were greatly affected by the strength or weakness of the arguments. This shows persuasion by the central route (much focus on argument content, little influence of superficial cues).
The peripheral route to persuasion involves little cognitive response and more "association" of superficial cues and conclusions urged. Persuasive communications of this kind would occur in contexts such as advertising, issues of little interest to the audience, or issues of low controversy. The central route, by contrast, involves a high degree of cognitive processing of the message content. Attitude change phenomena of this kind occurs when the audience has high interest, need, or ability regarding the substance of the message.
The jury trial is a situation that would seem to be almost ideal for maximizing the importance of central route processing to belief and attitude change. By virtue of their role, the formality of the proceedings, and the requirement that at the end of the day they make the decision, jurors would be highly motivated to understand and reach a correct conclusion about the substantive information presented. The information-heavy nature of trials and their adversarial nature insures that jurors will have considerable pro- and counter-argument resources from which to draw. Again, this would seem to make the jury trial one of the best opportunities to exercise thoughtful citizenship that we are likely to find in modern society. The fact that lawyers concern themselves with minutiae of how a witness looks or sounds or what degrees their expert witnesses hold may say more about the mistaken guesses of trial lawyers about how juries decide cases (peripheral route phenomena) rather than the processes by which juries most likely are influenced (central route phenomena).
More Specific Phenomena of Attitude Change
A long list of phenomena of attitude change studied in the context of or applicable to trials could be generated.10 Detailed and exhaustive examination of them is beyond the scope of this article. But the following sub-sections give the outlines of several of them that are more relevant to legal policy concerning juries (and less relevant to tactical choices by trial practitioners).
1. Order Effects
Order effects have been of interest to students of persuasion at least since Aristotle wrote his Rhetoric. With respect to internal order (one’s own case), is an advocate more effective using the climax strategy (strongest arguments last) or the anti-climax strategy (strongest arguments first)? With respect to gross order, is it better to present first or last?11 If nothing else is clear from the order effects research, it is that information presented in the middle has less impact than information presented at the beginning or the end.12
The greatest clarity that has been brought to the question of order effects in the trial context has provided by research by Thibaut & Walker.13 They found strong recency effects for both internal and gross order. Consequently, when each party exercises its classical preference for internal ordering (climax), and the conventionally required gross ordering is followed, the effects of order are largely canceled out. Thus, neither party gains an advantage.
The subject of order effects illustrates the way in which knowledge about juror persuasion can produce a situation where informed advocates acting in their self interest within a trial structure created by informed policy-makers can neutralize content-irrelevant effects (namely, who goes first), thereby allowing the influence of the content of the parties’ evidence and arguments to be maximized.
2. Effects of Legally Impermissible Information
Do jurors use legally impermissible information to reach their decisions?14 The short answer from experimental research is that often they do. Indeed, this may be one of the most popular topics for jury research: have some mock jurors decide cases with and others without certain forbidden information and look to see if a difference obtains. If so, you know the jurors used what they ought not to have used.15
Numerous examples can be offered on aspects of jury decision-making where the evidence suggests that jurors use information that they are instructed to disregard, or put evidence to a use for which they are instructed not to: (a) When informed about a defendant witness’s prior crimes for the permissible purpose of evaluating credibility, jurors use the information for the impermissible purpose of inferring the likelihood that the defendant committed the currently charged crime.16 (b) Mock jurors have been found to use the strength of evidence of liability to help them assess compensatory damages.17 (c) And they use evidence of punitive liability to judge compensatory liability.18 (d) When accomplices escape, jurors are more lenient toward the defendants who were caught.19 (e) Mock jurors deciding rape cases based their verdicts in part on the race, physical attractiveness, sexual history, and respectability of the victims.20 (f) Jurors rely on information gained from pretrial news coverage.21 (g) There is evidence of greater leniency toward defendants who are of low status,22 who are attractive (unless the attractiveness has been used to accomplish the crime),23 whose SES is higher,24 and who are not wearing prison garb or being attended by armed guards.25 (h) Studies of civil cases find that more attractive plaintiffs, white plaintiffs, and plaintiffs with higher family status, are awarded more in damages.26
In short, jurors react to information that the law regards as irrelevant to the decision at hand. But what are we to conclude from this about the utility of the jury as an instrument of trial decisions? First, we might ask: compared to what? Studies that take the trouble to compare the impact of extra-legal evidence with that of relevant, admissible evidence typically find the latter to be more important to jurors’ decisions. (See, e.g., Visher, supra note 1.) Jurors’ decision-making also should be compared to that by judges. Do judges do any better at disregarding inadmissible information or using otherwise admissible information inappropriately? Although far fewer studies have been conducted using judges, few if any of them suggest judges are any purer in their use of such information.27
Two basic cures for these problems are available. One is obvious: to the extent possible, prevent inappropriate information from reaching the jury. Some rules of evidence already exist to accomplish this, such as rules controlling character evidence or prior convictions. Indeed, juries provide the institutional device whereby this can be accomplished: a judge can be the gatekeeper who prevents certain inadmissible information from ever reaching the jury, thereby insuring that the jury’s decision is kept free of such influences.28
The second, and less obvious cure, is the provision of relevant, probative information to the jury. And it already is the central task of the trial lawyer to do precisely this. As we have seen elsewhere, the effect of irrelevant, inadmissible, or biasing information is reduced in its effect to the degree that relevant, probative evidence is available for the jurors’ consideration.
Consider the issue of differential responses of juries to defendants with deep versus shallow pockets. We have a number of ways we might understand a facial finding that juries award plaintiffs more when the tortfeasor has deep pockets. First is the methodological dilemma. In actual courts, the two sets of cases differ in many more ways than the defendant’s wealth, so we have problems of confounding. Where corporations or governments are defendants, the injuries typically are more serious (Peterson, supra note 26). Where similar injuries have been suffered, medical malpractice cases, compared to auto crash cases, involve more defendants, more experts, more complex evidence, more skillful plaintiff lawyers, among other differences.29 In mock jury experiments, where everything has been kept equivalent except whether the defendant is a mom-and-pop operation or a large corporation, and a difference in awards as a function of the nature of the defendants has been found, we confront issues of what accounts for the observed difference. Are jurors surcharging or discounting the award-that is, are they adding a surcharge to the awards assessed against corporate defendants or are they discounting the awards assessed against small defendants? (In other words, how does the ratio of plaintiff loss to the assessment against defendant 1 compared to the ratio of plaintiff loss to the assessment against defendant 2?) Or, finally, as research by Hans suggests,30 jurors might be making judgments of quite a different kind: where the defendant is a wealthy corporation, as compared to a mom-and-pop business, jurors infer that the corporation has the capacity to better predict, plan, and control the consequences of its actions, and therefore is more accountable for those consequences. In equity theory terms, the ratios the jury is comparing would appear to be the defendant’s ability to avoid harmful consequences versus the avoidance steps taken and the consequences that resulted.31
Interestingly, where the law is that jurors should take into account the defendant’s wealth, namely, in assessing punitive damages, the one experiment I know of on the question found that punitive damages did not differ as a function of whether the defendant was a wealthy corporation or a humble one (Diamond et al., supra note 17). This also suggests that the numerous states which have authorized bifurcation only of the amount of punitive damages, based on an assumption of special dangers associated with jurors learning about the worth of a defendant, appear to be relying on fear of an effect that is exaggerated or non-existent.32 At the same time, those states fail to protect defendants from the real risk of prejudice: providing evidence of punitive liability during the compensatory phase of the trial.
Conclusions
A consideration of the psychology of jury decision-making leads to three general lessons about juries. First, it appears that the common law jury trial appears to have evolved into a process that tends to maximize the sensible use of rational information. This becomes apparent when we consider available alternatives to or variations on the common law trial. Of the many ways to influence attitudes and beliefs-which are widely employed in various spheres of society-those available to advocates in trials are limited almost exclusively to the transmission of information, to rational persuasion.
Second, we are led to the question: "Compared to what?" The real issue is: from among several realistic policy choices, which is the best? Thus, all evaluations of the jury system must be in comparison to some practical alternative-other decision-makers, structures, procedures, and so on. To take the extreme example, the abolition of juries implies the use of other decisions-makers, such as judges or arbitrators or claims administrators. We cannot responsibly move to those alternatives without finding out in what ways those others decide cases better or worse than juries already do.
Third, the focus of jury reform should be not on the jurors themselves but on the procedural and evidentiary environment into which they are placed. Assuming there is not likely to be a retreat from the expansion of jury democracy, then it will be far easier to improve the performance of juries by making their task more manageable than by trying somehow to change the people who serve as jurors.
Notes
1. See, Shari S. Diamond, "Scientific Jury Selection: What Social Scientists Know and Do Not Know," Judicature 73 (Dec.-Jan.1989), 178; Valerie Hans & Neil Vidmar, Judging the Jury (1986); Reid Hastie, Steven Penrod & Nancy Pennington, Inside the Jury (1983); Michael J. Saks, "The Limits of Scientific Jury Selection: Ethical and Empirical," Jurimetrics Journal 17 (1976), 3; Christy A. Visher, "Jury Decision-making: The Importance of Evidence," Law & Human Behavior 11 (1987), 1. Also see Harry Kalven & Hans Zeisel, The American Jury (1966) (finding approximately 80% agreement between verdicts of judges and jurors).
2. Or should be. Those who don’t know, and who get unlucky, find themselves in a methodological pickle with a meaningless study. One example is Joan Kessler, "An Empirical Study of Six- and Twelve- Member Jury Decision-Making Processes," U. Mich. J. L. Reform 6 (1973), 712; critiqued by Shari S. Diamond, "Jury Experiment Reanalyzed," U. Mich. J. L. Reform 7 (1974), 520. (Among other problems, there was no variation in dependent variables because the case evidence was too lopsided).
3. For a start, see Philip Zimbardo & Michael Leippe, The Psychology of Attitude Change and Social Influence (1991).
4. Dyer v. MacDougall, 201 F2d 265, 269 (1952).
5. Miron Zuckerman, Bella DePaulo, and Robert Rosenthal, "Verbal and Nonverbal Communication of Deception," in L. Berkowitz (ed.), Advances in Experimental Social Psychology 14 (1981), 26. For a literature review focused more sharply on the courtroom situation, see, Gerald R. Miller & Judee K. Burgoon, "Factors Affecting Assessments of Witness Credibility," in R. Bray & N. Kerr, The Psychology of the Courtroom (1981), at 182-190.
6. Richard Petty & John Cacioppo, "The Elaboration Likelihood Model of Persuasion," in L. Berkowitz (ed.) Advances in Experimental Social Psychology 19 (1986), 123.
7. Anthony G. Greenwald, Cognitive Learning, "Cognitive Response to Persuasion, and Attitude Change," in A. Greenwald, T. Brock & T.M. Ostrom (eds.), Psychological Foundations of Attitudes (1968), 147.
8. Richard Petty, Gary Wells, & Timothy Brock, "Distraction Can Enhance or Reduce Yielding to Propaganda: Thought Disruption versus Effort Justification," J. Personality & Soc. Psy. 34 (1976), 874. Hecklers beware.
9. Richard Petty, et al., Personal Involvement as a Determinant of Argument Based Persuasion, J. Personality & Soc. Psy. 41 (1981), 847.
10. See the list in Michael J. Saks & Reid Hastie, Social Psychology in Court (1978), at 102-104.
11. The law has removed the choice by allowing the party with the burden of proof (prosecutors and plaintiffs) to go first and last.
12. See review in Saks & Hastie, at 105-107.
13. John Thibaut & Laurens Walker, Procedural Justice: A Psychological Analysis (1975), Ch. 7.
14. We should not fail to note that what information is legally extraneous is not always easy to say. For example, while in many circumstances gender might be thought to be an inappropriate consideration, the law regards it as relevant, for example, in deciding the non-economic value of facial disfigurement. It may be a valid consideration in a claim by a wife that she was coerced into committing a crime by a husband (but not a claim by a husband that he was coerced by his wife?). Similarly, should one’s socioeconomic status matter? Perhaps not directly. But perhaps so in drawing a chain of inferences involving knowledge, motives, resources, and so on. Below we will discuss yet another example involving defendants of differing wealth.
15. K.D. Gerbasi, M. Zuckerman & H. Reis, "Justice Needs a New Blindfold: A Review of Mock Jury Research," Psychological Bulletin 84 (1977), 323.
16. Valerie Hans & Anthony Doob, "Section 12 of the Canada Evidence Act and the Deliberations of Simulated Jurors," Criminal Law Quarterly 18 (1976), 235; Roselle L. Wissler & Michael J. Saks, "On the Inefficacy of Limiting Instructions: When Jurors Use Prior Conviction Evidence to Decide on Guilt," Law & Human Behavior 9 (1985), 37-48; Kerri L. Pickel, "Inducing Jurors to Disregard Inadmissible Evidence: A Legal Explanation Does not Help," Law & Human Behavior 19 (1995), 407.
17. E.g., Edith Greene, "On Juries and Damage Awards: The Process of Decisionmaking," Law and Contemporary Problems 52 (1989) 225; Dale W. Broeder, "The University of Chicago Jury Project," Neb. L. Rev. 38 (1959), 744, 757-59; Shari S. Diamond, et al., "The Effects of Bifurcating Claims for Punitive Damages in Product Liability Cases" (Unpublished Report to G.D. Searle Corp., 1995).
18. Diamond et al.
19. William DeJong, et al., "Effect of an Escaped Accomplice on the Punishment Assigned to a Criminal Defendant," J. Personality & Soc. Psy. 33 (1976), 192.
20. C. Jones and Eliot Aronson, "Attribution of Fault to a Rape Victim as a Function of Respectability of the Victim," J. Personality and Soc. Psy. 26 (1973), 415; D. Landy & Eliot Aronson, "The Influence of the Character of the Criminal and His Victim on the Decisions of Simulated Jurors," J. Experimental Soc. Psy. 5 (1969), 141; R.E. Smith, J.P. Keating, R.K. Hester & H.E. Mitchell, "Role and Justice Considerations in the Attribution of Responsibility to a Rape Victim," J. Research in Personality 10 (1976), 346.
21. C.C. Hoiberg & L.K. Stires, "The Effect of Several Types of Pre-Trial Publicity on the Guilt Attributions of Simulated Jurors," J. Applied Soc. Psy. 3 (1973), 267 (lurid details affected females in rape cases, but not males); Gary Moran & Brian L. Cutler, "The Prejudicial Impact of Pretrial Publicity," J. Applied Soc. Psy. 21 (1991), 345; Alice Padawer-Singer & Alan Barton, "The Impact of Prejudicial Publicity on Jurors’ Verdicts," in Rita Simon (ed.), The Jury System in America (1975); Rita James Simon, "Murder, Juries, and the Press," Transaction 3 (1966), 40; Stanley Sue & R.E. Smith, "How Not to Get a Fair Trial," Psy. Today 7 (May, 1974), 86 ("Jurors remember what the judge tells them to forget."); Stanley Sue, R.E. Smith & R. Gilbert, "Biasing Effects of Pretrial Publicity on Judicial Decisions," J. Criminal Justice 2 (1974), 163; Stanley Sue, R.E. Smith & G. Pedroza, "Authoritarianism, Pretrial Publicity, and Awareness of Bias in Simulated Jurors," Psy. Reports 37 (1975), 1299; S. Wolf & D.A. Montgomery, "Effect of Inadmissible Evidence and Level of Judicial Admonishment to Disregard on the Judgments of Mock Jurors," J. Applied Soc. Psy. 7 (1977), 205; Edith Greene & Elizabeth Loftus, "What’s New in the News: The Influence of Well-publicized News Events on Psychological Research and Courtroom Trials," Basic & Applied Social Psychology 5 (1984), 211; Rita James Simon, "Does the Court’s Decision in Nebraska Press Association Fit the Research Evidence on the Impact on Jurors of News Coverage?," Stanford L. Rev. 29 (1977), 515; Rita James Simon, "The Impact of Pretrial Publicity on the Jury, in Rita Simon (ed.), The Jury: Its Role in American Society (1980); Geoffrey P. Kramer, Norbert L. Kerr, and John S. Carroll, "Pretrial Publicity, Judicial Remedies, and Jury Bias," Law & Human Behavior 14 (1990), 409; Hedy D. Dexter, Brian L. Cutler & Gary Moran, "A Test of Voir Dire as a Remedy for the Prejudicial Effect of Pretrial Publicity," J. Applied Soc. Psy. 22 (1992), 819.
22. E.g., Robert M. Bray et al., "The Effects of Defendant Status on the Decisions of Student and Community Juries," J. Social Psychology 41 (1978), 256.
23. E.g., Harold Sigall & N. Ostrove, "Beautiful but Dangerous: Effects of Offender Attractiveness and Nature of the Crime on Juridic Judgment," J. Personality & Soc. Psy. 31 (1975), 410.
24. E.g., J.M. Gleason & V.A. Harris, "Group Discussion and Defendant’s Socio-Economic Status as Determinants of Judgments by Simulated Jurors," J. Applied Soc. Psy. 6 (1976), 186.
25. Francis Dane & Lawrence Wrightsman, "Effects of Defendants’ and Victims’ Characteristics on Jurors’ Verdicts," in N. Kerr & R. Bray (eds.), The Psychology of the Courtroom (1982); G. Fontaine & R. Kiger, "The Effects of Defendant Dress and Supervision on Judgments of Simulated Jurors," L. & Human Behavior 2 (1978), 63.
26. C. Stephan & J.C. Tully, "The Influence of Physical Attractiveness of a Plaintiff on the Decisions of Simulated Jurors," J. Soc. Psy. 101 (1977), 149; Mark A. Peterson, Compensation for Injuries: Civil Jury Verdicts in Cook County 34-37 (1984); also see studies reviewed in Dane & Wrightsman.
27. Stephan Landsman & Richard Rakos, "A Preliminary Inquiry into the Effect of Potentially Biasing Information on Judges and Jurors in Civil Litigation," Behavioral Sciences & the Law 12 (1991), 113; Gary L. Wells, "Naked Statistical Evidence of Liability: Is Subjective Probability Enough?," J. Personality & Soc. Psychol. 62 (1992), 739.
28. Of course, it would be possible, in principle, to do this with judges alone-one as gatekeeper and one or several as factfinders.
29. Neil Vidmar, Medical Malpractice Juries (1995).
30. Valerie P. Hans, "The Jury’s Response to Business and Corporate Wrongdoing," L. & Contemp. Probs., Autumn 1989, at 177.
31. E. Green, "The Reasonable Man: Legal Fiction or Psychosocial Reality?," L. & Soc’y. Rev. 2 (1967) 241 (varied precautions, degree of risk, extent of injuries; found that jurors ignored injuries but were sensitive to precautions and risks in assessing what was reasonable conduct).
32. For example, the Texas Supreme Court has reasoned: "Bifurcating only the amount of punitive damages...eliminates the most serious risk of prejudice, while minimizing the confusion and inefficiency that can result from a bifurcated trial." Transportation Insurance Company v. Moriel, 879 S.W.2d 10 (Tex., 1994).