Experimental Psychology: The Juror Experiment

The paper aimed at examining the influence of eyewitness testimonies on juror’s decision making in a criminal trial. The sample size of 100 participants was taken for all three eyewitness conditions (None, unrefuted, discredited). The participants who were eligible to be recruited in the study were adult jury members. A one-way ANOVA was used to establish how the testimony of an eyewitness impacts the verdict of a jury in a criminal trial. The independent variable was the eyewitness testimony and the dependent variable was the guilty rating. The results indicate that there was a significant effect of eyewitness testimony on guilt ratings given by participants. Also, the findings pointed out a significant difference between none and discredited eyewitness groups regarding guilt ratings, as well as between the none and the unrefuted witness group. Thus, the findings are important in determining how a jury makes decisions in criminal cases. 

Keywords: Eyewitness, Guilty rating, Jury 

Experimental Psychology: The Juror Experiment 

Introduction 

The jury verdicts directly affect hundreds of individuals in the United States every year. An offender can be convicted whenever the court finds him or her guilty of an offence. If the offender is not proven guilty, then the courts acquit him or her ( Binnall, 2018 ). Any criminal proceeding results in three possible outcomes. It may be a conviction of the innocent, guilty and acquittal of the innocent. Hence, at the end of any criminal court proceeding, any of the three possible outcomes is the conclusion. The evidence before the jury determines the direction a case takes (Lehmann, 2019). However, many aspects may influence the jury's verdict, such as race, gender, age, and ethnicity. Since the 1980s, various states have implemented their sentencing guidelines to create certainty in the sentencing outcomes to reduce unwarranted sentencing disparity and increase transparency (Jaitman & Anauati, 2020). The decision is informed by a series of evidences presented before the court. One of the pieces of evidence is eyewitness testimony, which is a very persuasive form of evidence in court proceedings. The juror experiment aimed at assessing the influence of eyewitness testimonies on a juror’s decision making in a criminal trial. 

Objective 

To determine how eyewitness testimony impacts juror’s decision making in a criminal trial. 

Specific objective 

To examine whether eyewitness testimony was influential on a jury in a criminal trial and if it affected a jury’s decision making in a trial over other forms of evidence, such as forensic, DNA evidence. 

Hypothesis  

Null hypothesis (H 0 ): The juror relies on the eyewitness testimonies of a credible witness in making convictions. 

Alternative hypothesis (H a ): The juror does not rely on the eyewitness testimonies of a credible witness in making convictions. 

Methods 

Participants 

A convenience sample of jury members was enrolled on the study. The sample size of 100 participants was taken for all three eyewitness conditions (None, unrefuted, discredited). A simple random sampling technique was used to recruit the participants into the study. The jury groups were assigned to each on the three conditions randomly, unrefuted (n=37), discredited (n=37) and none (n=26). The participants who were eligible to be recruited in the study were adult jury members. It excluded people who were not fluent English speakers. This study included participants of all ages and gender.  

Materials  

In this study, three eyewitness scenarios that are the none, discredited and refuted witnesses. The participants were then given an online questionnaire that asked the subjects about their views on the reliability of different types of testimony, such as expert testimonies and eyewitness testimonies. They were also asked about their views on science and vague opinions about the community. The subjects were exposed to a video of an armed robbery mock trial, which contained all forms of mentioned testimonies and all aspects relevant to an armed robbery criminal trial. Afterwards, the subjects answered a second post-trial questionnaire to give their opinions on the evidence they were shown. Thereafter, the juries were given time to deliberate their verdicts. Once the juries reached their verdicts, unanimous or hung, they filled out a final questionnaire discussing their reactions to the jury verdict and the deliberation process, and their knowledge about DNA evidence and jury reform. The survey had a total of four questions based on their age, gender, eyewitness condition and guilt rating. All the questions were closed-ended with a Likert scale.   

Procedure  

A 2 x 2 between groups experimental design was employed that included eyewitness condition (None, unrefuted, discredited) and guilty rating dependent variable. The one-way ANOVA was used to determine how the testimony of an eyewitness impacts the verdict or decision of a jury in a criminal trial. The independent variable was the eyewitness testimony that is a categorical variable measured in three categories: none, unrefuted, a discredited eyewitness. This resulted in three treatment conditions: 1) none witness, 2) unrefuted witness, and 3) discredited witness. The major dependent variables were measures of the perceived guilt rating of the defendant. The guilty rating responses were measured on a Likert scale of 7, where 1 represents innocent, and 7-guilty. The study was done online where the participants were recruited into the study through an email generated by the administrator. Before the study was conducted, the participants were given the consent form to sign to participate in the survey. The researcher assured them of information privacy and usage. All the participants experienced the same steps in the same order among all the conditions. Randomization was employed to assign each participant to one of the three conditions. The participants were subjected to all the three conditions. The experiment was conducted online, with each participant being sent the questionnaire via email. Every participant was required to fill the questionnaire alone. The entire procedure required an approximate period of 10 minutes.  

Results 

A one-way ANOVA test was conducted to examine the effect of eye-witness conditions. There were three levels, unrefuted eyewitness testimony, a discredited eyewitness testimony, and no eyewitness testimony (control group) on participant’s guilt rating on the defendant. There was a significant main effect of eyewitness testimony on guilt ratings given by participants, F (2, 62.7) = 5.39, p = 0.007, because the p-value is less than 0.05 ( p  < 0.05). The Post-hoc comparisons using the Tukey Post Hoc test indicated that there were no statistically significant differences in guilty ratings between none eyewitness (M = 4.73, SD=1.34) and unrefuted eyewitness group (M = 4.97, SD = 1.50), because the p-value = 0.83 is above 0.05. The difference in guilt ratings between None (M = 4.73, SD = 1.34) and Discredited (M = 3.70, SD = 1.88) was significant because the value 0.04 is less than 0.05. Further, there was a significant difference in guilt ratings between ‘unrefuted’ and ‘discredited’ was significant because 0.003 is less than 0.05.  

Eyewitness Condition

Figure 1. The figure highlights the effects of each level of eyewitness condition on the participants’ average guilt ratings. Blue is no eyewitness, grey is unrefuted eyewitness, yellow is discredited eyewitness. 

The chart above indicates that the participants with the none eyewitness condition have a slower guilty rating compared to others. The discredited and unrefuted participants exhibit a fairly close together guilt rating. 

Discussion 

The purpose of this study was to examine the influence of eyewitness testimonies on a juror’s decision making in a criminal trial. The findings indicate that there was a significant difference between the Eyewitness Conditions’ Guilt Ratings. Further analysis indicates a significant difference in guilt ratings between participants with none and discredited conditions. Also, participants unrefuted and discredited conditions significantly differed from the guilty rating. Hence, the eyewitness testimony plays a vital role in the guilty rating of the defendant and jury’s decision-making. The findings are important in determining how a jury makes decisions in criminal cases. 

Some of the problems experienced during the study is the lack of willingness for participants to take part in the study. Further, there is a small sample size that lowered the accuracy of the study, and the lack of deliberating groups. The limitations directly affected the study findings. To better answer the research question, I will consider increasing the sample size. Further, I will include other variables such as race and jury service to determine how they affect a jury’s verdict. The independent sample t-test will be used to examine the difference linking the guilty rating and other variables such as the gender of the participants. 

References 

Binnall, J. M. (2018). Summonsing criminal desistance: Convicted felons' perspectives on jury service.  Law & Social Inquiry ,  43 (1), 4-27. 

Jaitman, L., & Anauati, V. (2020). The dark figure of crime in Latin America and the Caribbean.  Journal of Economics, Race, and Policy ,  3 (1), 76-95. 

Lehmann, P. S. (2019). Race, ethnicity, threat, and the sentencing of transferred juveniles in Florida criminal courts. 

Ross, A., & Willson, V. L. (2017). One-way anova. In  Basic and advanced statistical tests  (pp. 21-24). Brill Sense.