The complex and multifaceted nature of human behavior can often make it challenging to predict how individuals will act in specific situations. To determine whether a juror may exhibit bias or make irrational decisions, it’s essential to have a comprehensive understanding of the context in which they will make their decision and the stable and enduring characteristics they bring to that setting. In a trial, we have access to the case details and are aware of the significant situational variables that come with any trial setting, such as the high-pressure atmosphere of rendering a verdict and the group dynamics among the jury. Furthermore, we understand that a juror’s individual characteristics (i.e demographic and psychographic information), can influence how they interact with these situational variables in predictable ways [1, 2].

While it may be easy to obtain demographic information about potential jurors, using such information to predict their behavior is problematic. Not only does this rely on stereotyping, but studies have shown little correlation between juror demographics and their decision-making behavior [3]. These findings may seem counterintuitive, as we all feel, to a certain extent, that our group memberships (i.e., our gender, our race, our socioeconomic status) impact how we view the world. The issue is not that demographic information is inconsequential but that it has little predictive power when used in isolation – there’s a lot more to a person than just their age, sex, or race, for instance. However, statistical analysis can help to understand better how a juror’s demographic and psychographic traits may interact with the specifics of a given case.

Psychographic information, particularly personality traits, should play a crucial role in developing trial strategies and selecting a jury. Personality traits are stable and enduring characteristics that influence how a person behaves in most situations [4]. The unique constellation of personality traits that a person possesses affects what information they pay attention to, how thoroughly they consider an argument, and how they cooperate and deliberate in a group setting [5, 6, 7]. While many perspectives on personality exist, trait models of personality, trait models are best suited to identifying individual differences in personality and using those results to make predictions about behavior. Popular trait models include the Myers-Brigg Type Indicator (MBTI), the Minnesota Multiphasic Personality Inventory (MMPI), and the Five-Factor Model. However, these models differ in their abilities to predict a juror’s behavior. For instance, while widely used among laypersons, the MBTI will often give completely different personality types for people if they take the test more than once [8]. The MMPI, in contrast, while statistically sound is most effectively utilized in a clinical setting, rather than for more general purposes [9]. In comparison to other extant measures, instruments that capture where participants fall on the “Big Five ” dimensions of personality (i.e., Extraversion, Neuroticism, Agreeableness, Conscientiousness, and Openness to Experience) have amassed an impressive body of empirical support [10, 11, 12]. As the Big Five model has been extensively studied and validated across a wide range of populations and settings, it is the most appropriate model to use when predicting juror behavior.

While the ideal juror is a blank slate, there is no “blank” personality. Given that all human beings fall somewhere on the dimension of each trait, that the Big Five personality traits have been able to predict a wealth of important real-world behaviors, and that these personality traits are stable across situations; it is inevitable that personality traits will impact jury decision-making. While we cannot find a blank slate of personality, we can use statistical analysis to predict the traits that have been found to make jurors more prone to biases, irrational decision-making, and groupthink.

1. Extraversion: Extraverts are typically outgoing, sociable, and assertive individuals who are comfortable in group settings. Research has shown that extraverts may be more likely to speak up during jury deliberations and may be more persuasive in convincing other jurors to adopt their views [13]. This can greatly impact deliberation, as an extraverted individual with a biased opinion can contribute greatly to groupthink. There is also evidence that extraversion is slightly associated with narcissism [14]. This is relevant to consider in a potential juror as they may be more likely to prioritize their own self-interests and to discount the opinions and perspectives of others.

2. Neuroticism: Individuals who score high in neuroticism are more likely to be anxious, worried, and sensitive to their emotions. This may make them more susceptible to confirmation bias, in which they selectively attend to and interpret information that confirms their pre-existing beliefs or biases [15]. Research shows that the use of heuristics, or mental shortcuts, is common when in a high-stress situation, such as jury deliberation [16]. If a juror’s baseline is already quite high, this could indicate they will be uniquely prone to errors and thinking that result when using cognitive shortcuts rather than more effortful decision-making strategies. Neuroticism is also correlated with emotional instability [17]. Emotional instability refers to the tendency to experience intense emotional reactions and mood swings. Jurors who are emotionally unstable may be more prone to making impulsive decisions based on their emotions rather than rational considerations of the evidence.

3. Agreeableness: In order to predict jury behavior, it is important to consider both individual-level decision-making and group-level decision making styles. Given the importance of group dynamic to decision-making, it is important to assess if potential jurors score high in agreeableness, meaning they are typically cooperative, empathetic, and eager to avoid conflict. While jurors high in agreeableness adapt to settings that require social cooperation, this penchant towards cooperation may trump their motivation towards critical thinking, making these individuals more susceptible to groupthink and conformity pressures [18, 19]. In a jury setting, conformity can lead jurors to adopt the majority opinion without critically evaluating the evidence. This can be particularly problematic in cases where the evidence is ambiguous or conflicting.

4. Conscientiousness: Conscientiousness individuals are typically responsible, organized, and reliable. Individuals who score high on this dimension are more likely to take their role as a juror seriously and may predispose a juror to be more thorough and systematic in their evaluation of evidence and may be more likely to adhere to legal instructions and standards of evidence [20, 21]. Those low on measures of conscientiousness tend to give little consideration to rules or moral obligation. This can mean they are less likely to follow instructions and more likely to rush a decision or be swayed by factors outside the evidence presented at trial [21, 22].

5. Openness to Experience: Individuals who score high in openness to experience are typically creative, curious, and open-minded; this trait is negatively correlated with prejudice [23]. Potential jurors who score high on openness are less likely to hold prejudiced beliefs or to view certain individuals or groups in a negative light. Jurors who hold prejudiced beliefs may be more likely to view certain defendants as guilty or to interpret evidence in a way that confirms their biases.

Overall, the current research suggests that personality traits can play a significant role in jury decision-making. However, as human behavior is complex, it is unrealistic to seek a single variable prediction of jury decision-making behavior. It is important to note that personality traits do not exist in isolation and may interact with each other to impact jury behavior. For example, a juror who is high in agreeableness and extraversion may be particularly persuasive in convincing others to adopt their views, while a juror who is high in openness and emotional stability may be more willing to consider alternative perspectives and evidence. Similarly, a juror who is low in conscientiousness and emotional stability may be less engaged and thorough in the deliberation process, potentially leading to a less informed and accurate verdict. By understanding how different personality traits impact jury behavior, how those traits interact with demographic information of both the defendant and the juror, and the specific details of the case, researchers and legal professionals can develop strategies to improve the accuracy and fairness of jury verdicts.


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