Factors that affect jury decision making

Michelle O'Brien

What key processes are involved in jury decision making?

Jurors are required to hear stories, or narratives, from both the prosecution and defense, and use all the information and evidence given as a basis for deciding a guilty or not guilty verdict. It was once thought that jurors made decisions, usually decision that are interpreted as important to due to the life determining nature, using careful, deliberate thinking. However, research has shown that instead of using a Bayesian form of decision making involving probabilities and likelihoods, that jurors make judgments based upon the facts or story having key characteristics of a narrative. In short, jurors tend to base decisions of the verdict based upon how convincing the narrative given by each side is in telling the story of how a crime happened.

Literature Review:

Most research has shown that decisions made by jurors in the courtroom setting are based upon the narrative discipline, meaning the extent to which the facts fit a story model, of the story teller. In a courtroom setting, the storytellers include the prosecution and defense, as well as the witnesses involved on both sides. Upon hearing testimony, jurors tend to create individual narratives of the facts given, which can be influenced by a variety of factors. These individual narratives are used in the decision making process of a guilty or non-guilty verdict based upon how convincing the evidence is in explain that the crime happened that way. The investigation by Hastie and Pennington was the first to address that decision making of jurors occurred through this method of thinking, not the Bayesian way of thinking in terms of probability.

Further research has shown that jurors generate these narratives and make a decision by constructing an explanation that accounts for the evidence in the form of a story, by learning verdict category attributes, and reaching a decision by classifying the story into the best-fitting verdict category. The narrative that each individual juror constructs is not based solely on evidence but also the characteristics of coherence, uniqueness, and goodness-of-fit of the story. The completeness of the story also plays a major role in decision making of a juror. Although it has been shown that jurors will use a linear model of anchoring and adjustment of their belief of guilt with each new piece of evidence, it has been shown that the overall completeness is the actual determinant of their decision.

Researchers have also investigated how the order evidence is presented and the deliberation style used affect the consistency and guilty verdict determined from the constructed narrative of the jurors. Deliberation style in the courts consists of whether the jurors, originating from a community setting, make their decisions using a verdict-driven or an evidence-driven style of deliberation. It was found that when juries were told to use verdict-driven deliberation, the jurors created a more pro-prosecution narrative when the defense’s case was presented in story-order, while jurors in the evidence-driven deliberation condition tended to form more consistent pro-prosecution stories when the prosecution's case was presented in story-order. Therefore, while it is important that information is given in story order in order to create the most consistent narratives amongst jurors, it is the method of retrieval, through deliberation, of this information that has more significant effects the jury’s verdict decisions.

Research into how to combat the inconsistencies between each juror’s narratives has shown that prosecutors and defense attorneys should hire litigation consultants. By hiring these consultants, both parties can learn more about how people make decisions in the trial setting , as well as being informing of how jurors acquire, remember, and process pieces of information in the trial. This type of consulting is a realistic step in improving the accuracy of jurors’ decision making by informing the source of the information on how to display the evidence in the proper manner to decrease the mistakes made by jurors.

Furthermore, research has begun to move towards developing a pretrial juror test, known as the Pretrial Juror Attitude Questionnaire (PJAQ), in order to eliminate some of the bias in jurors that cause error in story construction and the decision making process. This test has shown predictive validity in identifying characteristics of jurors including: confidence, proneness of conviction, innate criminality, and racial bias. By eliminating jurors that are high in these areas, some research has shown jurors construct more consistent and informative narratives that contribute to good decision making.

Relationship to Other Topics:

It seems that there is no realistic way to teach juror’s, especially because of the high demand and turnover rates, how to think in Bayesian terms of probabilities and likelihoods for making a decision. However, the creation of narratives seems to actually be an effective way to organize the large volumes of facts that are present within a trial. The combination of a limited cognitive capacity and limited working memory make the formation of a narrative necessary to understanding the evidence and other information encountered.

Much of the research on jury decision making relates to how the information is represented to the jury. While given the exact information, each juror represents that information in their own way and constructs their own story. The structures of the stories are determined by individual’s schemas and scripts that have been acquired over the course of development. It is here that individual differences can be minimized by making changes to better control the way in which jurors construct their story so that the narratives become more consistent across people. Juror’s stories are affected by many different aspects, including the representative heuristic and stereotypes. Similar to many decision making processes, the representative heuristic and availability heuristic affect which information is remembered and encoded into the jurors narrative of the facts given. Therefore, it is important to improve the narratives by both the defense and prosecution deemphasizing certain characteristics of the crime that fit common stereotypes in ways that work to their own advantage.

Therefore to solve the problems of jury decision making and begin working toward better decision making, the way in which the narratives are used in the process needs to be modified. One possible solution is to ask the jurors to write their narratives down individually and then compare within the group to catch and discuss discrepancies between the depictions of the trial that may have otherwise gone unnoticed. The method would provide more checks and balances to ensure that the proper narrative is being discussed and it would decrease some of the biases generated within the individual.


Finkelman, J. (2010). Litigation consulting: Expanding beyond jury selection to trial strategy and tactics. Consulting Psychology Journal: Practice and Research, 62(1), 12-20.

Hastie, R., & Pennington, N. (2000). Explanation-based decision making. Judgment and decision making: An interdisciplinary reader (2nd ed.) (pp. 212-228). New York, NY US: Cambridge University Press.

Lecci, L., & Myers, B. (2008). Individual differences in attitudes relevant to juror decision making: Development and validation of the Pretrial Juror Attitude Questionnaire (PJAQ). Journal of Applied Social Psychology, 38(8), 2010-2038.

Pennington, N., & Hastie, R. (1992). Explaining the evidence: Tests of the Story Model for juror decision making. Journal of Personality and Social Psychology, 62(2), 189-206.

Pennington, N., & Hastie, R. (1993). Reasoning in explanation-based decision making. Cognition, 49(1-2), 123-163.

Reardon, M. (2009). Jury decision making and the story model: How do deliberation style and evidence order influence the story that juries create? Dissertation Abstracts International, 70.