Juries play a critical role in the justice system, tasked with making decisions that have life-changing consequences for the accused, victims, and their families. The ideal jury should be composed of individuals who are impartial and unbiased in their decision-making. However, the reality is that group decision-making in the jury room is a complex process, influenced by a wide range of factors that can often leave group members more highly motivated towards achieving concurrence than engaging in sound decision-making [1].

In this article, we will explore the concept of groupthink and its antecedents in the context of a legal trial. We will also discuss the use of psychometrics, which refers to measures of individual difference variables such as personality, attitudes, and values, in identifying potential jurors who may be prone to dysfunctional or irrational decision-making.

The Fundamentals of Groups

Defining a group may seem like a simple task, but through the lens of social psychology understanding ‘the group’ is complex, nuanced, and often unpredictable. Although many people assume that the effectiveness of a group is simply a reflection of the abilities of its individual members, this is not always the case [2]. For example, if you want to make wise decisions regarding foreign policy, you might assume that assembling a team of leading experts in foreign policy would be a surefire tactic. Similarly, if you want to ensure that a verdict is unbiased, you might assume that such a result is assured as long as each individual juror is capable of objective decision-making.  However, even when we make these efforts, we can still see group failures. The Bay of Pigs disaster is a prime example of how even the most renowned foreign policy experts can fail when working in a group. Likewise, carefully selected jurors may still make subjective decisions based on superficial aspects of a case rather than conducting an objective review of the facts. Social psychology is rife with research geared towards understanding the phenomenon whereby a group functions worse than the sum of its parts. Psychological research on group processes has been particularly productive in its study of two core phenomena: group polarization and groupthink. 

Group Polarization

Group polarization occurs when the opinions and attitudes of individuals in a group become more extreme after group discussion [3, 4]. Studies on juries have shown that juries tend to arrive at higher punishment ratings and dollar awards than individual jurors prior to deliberation, indicating the occurrence of group polarization [5]. One explanation for this phenomenon is the persuasive arguments theory, which suggests that the more persuasive and numerous the arguments presented to group members, the more extreme their attitudes become [6, 7]. The trial setting is particularly conducive to group polarization because it involves exposure to a large number of persuasive arguments followed by sustained group discussion.

How can psychometrics help?

To ensure fair jury selection, it is crucial to identify both explicit and implicit biases of potential jurors. Although oral voir dire can reveal explicit biases, it is insufficient because people can also hold unconscious attitudes or stereotypes, known as implicit biases, that affect their decision-making [8]. Social psychology research has demonstrated the existence of implicit biases, and collecting psychometrics can be an effective method for identifying potential jurors who may be more susceptible to these biases [9, 10].

Without subjecting jury selection to the rigor of the scientific method, there is a risk of selecting jurors who hold subtle, implicit biases. These biases can manifest in several ways, such as when a juror processes the arguments presented during trial. Arguments that align with the juror’s preexisting stereotypes are likely to be perceived as more persuasive and encoded more deeply [11]. During deliberation, these biases can be further strengthened through group discussion.

Therefore, using psychometrics to identify individuals who may hold unconscious biases is crucial in avoiding biased decision-making. However, it is essential to note that bias is not the only factor that must be considered when selecting jurors to ensure that the group arrives at a fair and just verdict. Other individual difference variables (e.g., personality traits, cognitive abilities, attitudes, values) must also be identified to prevent poor group decision-making.


Humans have a deep-seated, biologically based propensity to operate cohesively in groups. This natural inclination can be advantageous, but it can also lead to negative outcomes, such as groupthink [12]. Groupthink is a decision-making style characterized by an excessive tendency among group members to seek concurrence [13]. The pursuit of consensus often supersedes the pursuit of making sound judgments. This phenomenon can explain how a collective group of unbiased jurors can arrive at biased and irrational decisions.

There are several factors inherent to the format of a legal trial that can contribute to groupthink:

1. High cohesiveness: Group cohesion, or the strong emotional attachment and desire for unanimity among group members, can be heightened in the emotional and pressure-filled environment of a trial. Jurors may feel loyalty to their fellow jurors or pressure to conform to avoid conflict or being seen as an outsider, potentially leading to a rushed verdict without sufficient consideration of all evidence.

2. Lack of Diversity and Isolation: Juries often lack diversity in experiences, backgrounds, and perspectives, making it easier for members to conform to dominant perspectives. Despite efforts to promote diversity in jury selection, juries often remain homogenous (e.g., jurors are disproportionately white, affluent, and socially privileged). Additionally, jurors are isolated from outside perspectives while deliberating, increasing the likelihood of groupthink.

3. Directive Leadership: A dominant, persuasive leader can suppress dissenting opinions and critical evaluation of evidence. This is a risk factor for legal contexts, as jurors may also be selected based on their willingness to follow instructions, reinforcing directive leadership.

4. Unsystematic Procedures: The lack of structured decision-making procedures in juries, combined with varying levels of experience and potential biases of jurors, can lead to reliance on cognitive shortcuts rather than critical thinking and objective evaluation of evidence.

5. Stressful Situations: Stress and anxiety can increase the likelihood of groupthink in decision-making situations. As the responsibility of making life-altering decisions can be a highly stressful experience, this represents a further risk factor for juries engaging in groupthink. Feeling a sense of urgency to arrive at a unanimous decision can result in a high value being assigned to conforming to the perceived group norms. As a result, self-censorship and suppression of alternative viewpoints can occur during deliberation.

How can psychometrics help?

Taken together, understanding the demographic and psychographic makeup of a jury is vital for diagnosing the likelihood that a jury will be “infected” with the “social disease” of groupthink.

While it is important to avoid creating a homogenous jury in terms of age, gender, race, or socioeconomic status, other individual difference variables can also impact a potential juror’s contribution to the deliberation process. By using psychometric measures to assess psychographic and demographic information, it is possible to predict whether a potential juror is likely to be domineering or passive, susceptible to individual biases, or possess personality traits that could impact their ability to make objective and impartial decisions. Assessing implicit biases based on race, gender, age, etc., which can be pervasive and impactful, but difficult to identify through traditional voir dire methods, can also contribute to creating a well-functioning jury that is less prone to groupthink.


To avoid groupthink in the jury room, it is essential to understand the complexities of group decision-making. By using advanced statistical techniques and big data, potential biases in group dynamics can be identified and proactive measures taken to prevent groupthink from occurring. A key factor in mitigating the risk of irrational and dysfunctional group decision-making is understanding the demographic and psychographic makeup of the jury pool. This enables jury selection decisions to be made with diversity in mind, reducing the risk of homogeneity in beliefs, values, and personalities.

Given the propensity of certain individuals and certain groups to engage in maladaptive decision-making, selecting unbiased jurors is essential to ensuring a fair trial. However, oral voir dire alone has limited utility in preventing the formation of these concerning group dynamics. For instance, individuals predisposed to conformity are more likely to contribute to a group dynamic with a high probability of poor decision making. If the data suggest that individuals high in introversion are prone to conformity, you may want to consider avoiding selecting those individuals. However, consider the limitations if your only measure of introversion is standing in front of a room and saying, “I consider myself the life of the party. Can you put your hand up if you strongly disagree with that statement?”. The data would suggest that the individuals you are trying to identify as conformists will conform in this setting; it is more likely that you will be assessing the traits of the most assertive members of the group that more submissive members are conforming with. It is well-documented in social psychology research that many aspects of the voir dire setting are likely to result in jurors responding dishonestly and inaccurately [14].

The limitations and potential for biased responding introduced by the voir dire setting speaks to the importance of using a supplemental juror questionnaire (SJQ) as an alternative method. By affording jurors a sense of anonymity, and removing the social desirability demands inherent in voir dire, an SJQ can gather responses that better reflect their true attitudes. Using an SJQ not only improves the accuracy of information but also provides more detailed information about potential jurors. This can help eliminate jurors who are prone to bias, group polarization, and groupthink. 

Contrary to popular belief, groupthink is not an unavoidable aspect of group decision-making. It is only pervasive when certain contextual and individual variables are present. By applying empirical methods to jury analysis, it is possible to identify the types of jurors that better approximate the ideals upon which juries were intended to fulfill. This includes a diverse group of individuals who can set aside personal biases and preconceptions to weigh the evidence presented in a logical and rational manner. By prioritizing diversity and utilizing psychometrics to predict group dynamics, we can create a well-functioning jury that is less prone to groupthink and more likely to arrive at just decisions.


  • Parkinson, S., & Baddeley, M. (2010). Group decision-making: An economic analysis of social influence and individual difference in experimental juries. The Journal of Socio-Economics, 41(5), 558-578. https://doi.org/10.1016/j.socec.2012.04.023   
  • Woolley, A. W., Chabris, C. F., Pentland, A., Hashmi, N., & Malone, T. W. (2010). Evidence for a collective intelligence factor in the performance of human groups. Science, 330 (6004), 686-688. https://doi.org/10.1126/science.1193147 
  • Moscovici, S., & Zavalloni, M. (1969). The group as a polarizer of attitudes. Journal of Personality and Social Psychology, 12(2), 125–135. https://doi.org/10.1037/h0027568 
  • Schkade, D., Sunstein, C. R. & Kahneman, D. (2000). Deliberating about dollars: The severity shift. Columbia Law Review, 100(4), 1139-1175. 
  • Vinokur, A., & Burstein, E. (1974). Effects of partially shared persuasive arguments on group-induced shifts: A group-problem-solving approach. Journal of Personality and Social Psychology, 29(3), 305–315. https://doi.org/10.1037/h0036010
  • Levinson, J. D., Cai, H., & Young, D. (2010). Guilty by implicit racial bias: The Guilty/Not Guilty Implicit Association Test. Ohio State Journal of Criminal Law, 8, 187-208.
  • Chen, P. G., & Palmer, C. L. (2017). The prejudiced personality? Using the Big Five to predict susceptibility to stereotyping behavior. American Politics Research, 46(2), 276-307. https://doi.org/10.1177/1532673X17719720
  • Rubinstein, R. S., Marshall, M., Jussim, L., & Honeycutt, N. (2023). Effects of individuating information on implicit person perception are largely consistent across individual differences and two types of target groups. Current Research in Behavioral Sciences, 4, 100090. https://doi.org/10.1016/j.crbeha.2022.100090
  • McKimmie, B. M., Masters, J. M., Masser, B. M., Schuller, R. A., & Terry, D. J. (2013). Stereotypical and counterstereotypical defendants: Who is he and what was the case against her? Psychology, Public Policy, and Law, 19(3), 343–354. https://doi.org/10.1037/a0030505
  • Janis, I. L. (1982). Groupthink. Houghton Mifflin.