Jury Decision Making
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Jury Decision Making

The State of the Science

Dennis J. Devine

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eBook - ePub

Jury Decision Making

The State of the Science

Dennis J. Devine

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About This Book

While jury decision making has received considerable attention from social scientists, there have been few efforts to systematically pull together all the pieces of this research. In Jury Decision Making Dennis J. Devine examines over 50 years of research on juries and offers a “big picture” overview of the field. The volume summarizes existing theories of jury decision making and identifies what we have learned about jury behavior, including the effects of specific courtroom practices, the nature of the trial, the characteristics of the participants, and the evidence itself. Making use of those foundations, Devine offers a new integrated theory of jury decision making that addresses both individual jurors and juries as a whole and discusses its ramifications for the courts. Providing a unique combination of broad scope, extensive coverage of the empirical research conducted over the last half century, and theory advancement, this accessible and engaging volume offers "one-stop shopping" for scholars, students, legal professionals, and those who simply wish to better understand how well the jury system works.

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Publisher
NYU Press
Year
2012
ISBN
9780814725221

1
The Lay of the Empirical Land

How many jury trials would you guess occur in the world each year? Ten thousand? One hundred thousand? A million, maybe? Well, no one knows for sure, but the number is certainly large. The first systematic attempt to estimate the number of annual jury trials in the United States appears to have been made by researchers associated with the Chicago Jury Project, who tried to determine the number that occurred in 1955. Obtaining a precise tally proved much more difficult than expected, as some jurisdictions didn’t keep records, others didn’t keep good records, and still others didn’t respond to the query. In the end, after more than a year of sleuthing, Kalven and Zeisel (1966) estimated that 55,670 jury trials were completed in the United States during 1955, with perhaps another 20,000 initiated and terminated. Since then, other estimates have been offered that range from 150,000 to 300,000 (Abramson, 1994; Hastie, Penrod, & Pennington, 1983; Kassin & Wrightsman, 1988).
The best and most recent estimate of the number of annual jury trials in the United States, though, comes from a massive study conducted by the National Center for State Courts (NCSC). Based on data from the “State-of-the-States” survey research project collected from all fifty states and the District of Columbia, researchers estimated that 148,558 jury trials were held in state courts in 2006 along with an additional 5,463 in the federal district courts (Mize, Hannaford-Agor, & Waters, 2007). Combining these two numbers yields a total current estimate of about 154,000 jury trials each year in the United States. Of these, about 47 percent appear to be for felony crimes, 19 percent for misdemeanor crimes, and 31 percent involve civil lawsuits, with 4 percent listed for “Other.” These jury trials involve around 32 million summons for jury duty and more than 1.5 million empaneled jurors. Although some commentators have lamented the perceived decline of the American jury, these numbers do not suggest that juries are going the way of the dinosaur any time soon.
In addition, many jury trials occur each year outside the United States. A handful of countries use juries composed entirely of laypersons as is done in the United States (e.g., Australia, Canada, England, New Zealand, Russia, and Spain). A few others use a mixed “escabinado” system in which juries are composed of both laypersons and judges or magistrates (e.g., France, Germany, Italy, Japan, and Poland). Unfortunately, we have no good estimate of their frequency, with numbers notably absent from the most comprehensive source of information on world jury systems (Kaplan & Martin, 2006). It isn’t clear how many jury trials occur in these various countries each year, but the number is certainly much smaller than the corresponding figure for the United States (perhaps several thousand). Regardless of the precise value, it is important to keep in mind that juries are not unique to the U.S. and the number of jury trials taking place outside the United States each year is not inconsequential.

Jury Research 101

How Many Jury Studies Are Out There?

A jury study is viewed here as a formal, quantitative analysis of data collected systematically from a large sample of participants for the purpose of yielding broad generalizations about juror or jury decision making. Just as there are challenges associated with obtaining a precise estimate of the annual number of jury trials, there are obstacles to getting an accurate tally of the number of jury studies in existence. For starters, there is some question as to what should be counted. Some data collection efforts yield multiple publications; is each of these publications a study, or is it just one big study with its results divided up? This is not a critical question given the relatively small number of datasets that turn up in multiple publications, but my view is that jury studies should be defined by their datasets. There are other challenges beyond what to count, though. Scholars and scientists who study juries operate in a variety of professional disciplines and publish their research in a large number of professional outlets, including some two hundred law journals and more than fifty social science journals. Any effort to identify (much less collect) every published study of juries is bound to miss some. Many jury studies are also never published for one reason or another, including suspect methodologies, prosaic findings, or lack of author inclination. Finally, like New York City, jury scholars never seem to sleep—the number of jury studies is growing all the time.
All the same, a ballpark estimate of the number of existing jury studies would be useful for conveying some sense of the magnitude of the existing literature and the rate at which it is increasing. An early count by Bray and Kerr (1979) yielded seventy-two studies involving mock jurors, sixty of which were published after 1970. Most of these early studies were done in laboratory settings (70%) using written (54%) or audiotaped (29%) trial materials, and about half featured deliberation (52%). Two decades later, Nietzel, McCarthy, and Kerr (1999) tallied all studies involving jurors or juries that appeared in ten leading U.S. journals (most of them in the social sciences) between 1977 and 1994. They identified 265 studies published in this eighteen-year interval, or an average of about fifteen studies per year. Two journals accounted for nearly two-thirds of the publications—Law and Human Behavior (40%) and Journal of Applied Social Psychology (25%). The vast majority of studies (89%) dealt with criminal as opposed to civil matters, and the most frequently studied topic was the performance of witnesses (20%).
These search results were updated and extended by Greene et al. (2002), who examined two additional years of content (i.e., 1998 and 1999) in the ten journals surveyed by Nietzel et al. and also cataloged the contents of an unspecified number of additional journals that published jury research for the entire 1977–99 period. This added a sizeable number of studies to each year’s total, sometimes doubling (or more) the number found in just the ten leading U.S. journals. Greene et al. did not report the total number of publications they found but provided a three-dimensional graph that shows a clear upward annual trend and suggests (by my reckoning) that about 825 studies of juror or jury decision making were published between 1977 and 1999.
Merging the results of these literature surveys, and assuming that some were missed, it would seem that there were about 850 studies on juries published before 2000. Using the mean number of annual jury studies published in the last few years of the time span covered by Greene et al. (2002) as a starting point (51) and adding a few more per year for good measure, approximately 650 jury studies would have been published between 2000 and 2010. All told then, 1,500 is a plausible estimate of the number of published jury studies by the end of 2011. This value is doubtless an underestimate of the total number of formal jury studies conducted, with perhaps as many as half of those never published. Nonetheless, two things are very clear: (1) There is a great deal of existing research on juries available to consider, and (2) Efforts to conduct a comprehensive review of jury research are doomed to failure. Some level of selectivity will be required for any review.

Types of Jury Studies

Jury studies vary along many dimensions, including: (1) research design (experimental v. nonexperimental); (2) research setting (e.g., laboratory v. field); (3) participant type (e.g., students, community members, actual jurors); (4) trial format (e.g., case summary, edited transcript, audiotape, videotape, actual trial); (5) realism (e.g., inclusion of opening statements, jury instructions, deliberation); and (6) level of analysis (i.e., juror or jury). The various combinations allow for a dizzying variety of study profiles, but in practice only a few configurations occur with much frequency. Specifically, most jury studies fall into one of five categories: (1) analyses of archival data representing compilations of jury decisions across time and/or jurisdictions; (2) post-trial surveys of ex-jurors, attorneys, or judges collected via paper-and-pencil or the Internet; (3) post-trial interviews with real jurors; (4) field experiments assessing the impact of some procedural rule or instruction on actual juries; and (5) laboratory experiments that simulate a real trial and employ undergraduate students or community members as mock jurors. The first four categories represent different forms of field research based on real trials, whereas the latter two involve experiments that feature the manipulation of independent variables and (usually) random assignment of participants to study conditions. Of the jury studies published thus far, at least two-thirds represent mock jury experiments. The remaining third are based on actual trials, with about half of those representing some form of archival analysis and most of the rest involving post-trial surveys. Only a few studies feature in-depth interviews with real jurors or true field experiments with actual juries, primarily because they are so difficult to do.

Outcome Variables

The focal outcomes used in jury studies can be grouped into three major categories based on their chronological ordering: predeliberation, deliberation, and postdeliberation. Predeliberation outcomes correspond to the cognitive states of jurors before any group interaction. The flagship variable in this category is the juror’s preferred verdict immediately after exposure to the trial-related materials. Verdict preferences are often measured in terms of discrete choices (i.e., guilty v. not guilty) but sometimes using a continuum of culpability or responsibility. When aggregated to the jury level, individual verdict preferences yield a distribution of jurors who favor different verdict options prior to deliberation (e.g., nine who favor guilty, three who favor not guilty). One characteristic of a juror’s preferred verdict is the degree of confidence associated with it. Verdict confidence measures typically feature continuous response scales involving a subjective probability estimate. Other predeliberation variables include the extent to which jurors can recall case facts and the degree to which jurors comprehend their legal instructions. Recall and comprehension are often measured using a multiple-choice test but occasionally with open-ended short-answer items.
A second category of outcomes is associated with what happens during deliberation. One cluster of variables has to do with the foreperson—how this person is selected, when the selection takes place, and his or her demographic characteristics. A second cluster concerns the participation of jurors during discussion. Participation can be measured in various ways, including the number of times a juror speaks, the cumulative number of words spoken during deliberation, or the relative proportion of speaking acts or words accounted for by each juror. A third cluster corresponds to the assessment of individual opinions of members during deliberation via polling (i.e., “voting”), particularly the timing of the first poll, the number of polls taken in total, and whether polls are conducted openly or in some anonymous fashion. These variables are measured retrospectively by asking respondents to report what was done by the jury, or by videotaping simulated jury deliberations. A fourth cluster of deliberation variables pertains to the content of the jury’s discussion. Various coding schemes can be used to categorize what jurors say, and then counts can be obtained for each category and relative proportion measures created by dividing the number of statements of each type by the total number of statements made by the jury. Yet another cluster of deliberation variables is associated with jury performance—how well the jury fulfills its focal task of deliberating. Measures of deliberation quality include: (1) the thoroughness of the jury’s review of the evidence, (2) how well the jurors understand their instructions, (3) the extent to which deliberation is characterized by broad participation and input from members, and (4) the degree to which a positive, constructive atmosphere characterizes the jury room. Although it has not received a great deal of attention from researchers thus far, jury performance is important because of the strong relationship it should have with accuracy—in other words, juries that deliberate better should be more likely to reach the correct decision.
Postdeliberation outcomes represent a third category of variables relevant to jury research. Far and away, the most frequently studied variable in this category is the verdict reached on one or more charges (or claims) against the defendant, with probably 95 percent of the studies conducted on jury behavior employing verdicts as the focal outcome. In civil trials where the defendant is found liable for damages, juries also determine the amount of money to be awarded to the plaintiff for compensatory and (occasionally) punitive purposes. In criminal trials involving capital crimes, juries also decide the punishment or sentence as well (i.e., death v. life in prison). Separate from the party favored by the jury’s decision, another important outcome that has received surprisingly little attention from scholars is whether the jury’s decision is accurate—in essence, whether the jury “gets it right.” Accuracy from a legal perspective amounts to whether a jury arrives at the decision that would be legally appropriate given the relevant case facts and correct application of the relevant law. Of course, it is difficult if not impossible to determine jury accuracy with certainty in most real-world trials, but it can be approximated through various means. For instance, jury decisions can be compared with the opinions of objective legal experts such as the presiding judge or an appellate court. Another proxy indicator of accuracy is whether jury decisions can be viewed as legally defensible by objective legal experts given the most favorable interpretation of the facts established at trial.

Study Quality

Two primary criteria serve as benchmarks for assessing the value of any study: the degree to which accurate conclusions can be drawn about what causes what (causality), and the degree to which observed effects or relationships can be expected to hold in other settings (generalizability). These two criteria have been referred to as internal validity and external validity (respectively), and a number of considerations affect inferences about causality and generalizability in studies of jury decision making.
The ability to draw accurate conclusions about causality is primarily a function of a study’s research design. Basically, stronger inferences are warranted when independent variables are manipulated effectively, when participants are randomly assigned to levels of the independent variable, and when a high level of control exists over known or suspected extraneous (confounding) variables. Control can be achieved by either holding constant the potential confounding variables or, less optimally, by measuring them and removing their effects statistically during the analyses. Whether achieved via the design or the statistical analyses, the purpose of control is to rule out alternative explanations for the observed findings that do not involve the independent variables. A study’s sample size is also an important determinant of quality. In essence, a large number of observations (either individual jurors or juries) is needed to minimize sampling error, or the discrepancy between the numbers obtained from a sample and what is true in the overall population of jury trials. Sampling error occurs to some extent in any research study where the entire population is not examined but, other things being equal, the smaller the sample used in a study, the more the sample value can deviate from the true population value. As a result, larger studies are more trustworthy than smaller studies. Finally, the quality of a study’s manipulations and measures is also a critical determinant of internal validity. If study variables are conceptualized loosely, manipulated weakly, or measured poorly, it is simply difficult to interpret any findings (or non-findings) that emerge.
Likewise, several factors affect our confidence that a study’s results will generalize to other settings (e.g., real-world trials, or trials in other jurisdictions). Two important determinants of generalizability with regard to jury studies are realism and the type of participants involved. Realism basically concerns the degree to which a study incorporates elements of an actual jury trial, with the most important of these being a visual medium, opening and closing statements by the attorneys, a question-and-answer format for presentation of the evidence, cross-examination, formal jury instructions, and the opportunity to deliberate and reach a group decision. Research findings are usually more generalizable when they are based on real trials and actual jurors, although studies based on simulated trials involving mock jurors can offer a high degree of generalizability under some circumstances. Even when a study involves real trials and actual juries, observed findings cannot be assumed to hold automatically in other jurisdictions, as unique influences may be operating in the setting where the data were gathered. Thus, generalizability is usually greatest when real juries are studied across multiple jurisdictions and trial types (i.e., focal charges), which limits the possibility that study findings are restricted to a particular locality, court system, or kind of trial.

Trade-Offs

No study is perfect; all have some weakness. Of special note, the ability to draw causal inferences and the ability to generalize study findings are inversely related to one another. Essentially, the high degree of control needed to rule out alternative explanations and achieve good internal validity usually comes at the cost of lowering the realism of a study and thus reducing external validity. In particular, tightly controlled experimental studies that allow strong causal inferences must usually be conducted in laboratory settings with simulated trial materials and mock jurors. Any findings associated with these “unnatural” environments could be due to the unique experimental context. In contrast, nonexperimental field research typically features much less control over the research context but greater realism. The primary weakness of most field studies with real juries is the possibility that observed results are due to the nature of the case, the characteristics of the participants, or (most critically) the quantity and quality of the evidence presented as opposed to the focal variables. It is very difficult to attain both high control and high realism in the same study, so researchers usually must choose their poison. The inherent trade-off between internal and external validity highlights the importance of conducting multiple studies with complementary strengths and offsetting weaknesses.

Quality Continuum

While no study is perfect, they are not all equal either—some are better than others. Indeed, the many studies on juries fall on a continuum of study quality, with a distribution roughly bell-shaped in form. There are a few fantastic studies, some that are quite good, many that are moderate in quality, some with value but constrained by notable limitations, and a few that would better serve the field if they had never been done.
There are also some general tendencies with regard to the quality of different types of studies. Case studies focusing on one jury are at the low end of the quality continuum, at best leading to working hypotheses about how juries in general do things. Somewhat higher on the quality continuum are archival studies that involve compiling and analyzing distributions of jury verdicts or damage awards in one or more jurisdictions over some period of time. These studies have the benefit of involving real jury decisions, but usually suffer from poor (or missing) measures of important variables and are subject to alternative explanations associated with extraneous variables. The majority of jury studies—and those exhibiting the greatest range of quality—involve simulated trials and mock jurors. Many of these studies have only modest value due to a conjunction of undesirable attributes—abbreviated trial materials (e.g., case summaries), student mock jurors, and no deliberation. However, there are also some very good laboratory experiments that feature excellent control along with realistic trial depictions, representative participants (e.g., community residents, actual venirepersons, or jurors), and a deliberation component. These high-quality mock jury studies allow for strong inferences about focal independent variables, and their relatively high realism affords some confidence that their results will apply to real juries. All other things being equal, though, field experiments represent the best jury studies in that they combine high levels of experimental control and realism. Indeed, if there is an “ideal” jury study, it would probably be a field experiment with a large sample of real juries from multiple jurisdictions where one or more focal variables (e.g., trial practi...

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