How Do Eye witness Testimonials Affect Jury Decision Making

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A mock-jury scenario was conducted to evaluate the effects that eye-witness testimonies had on 139 participants. In order to study the true affects the testimonies have on decision making process, eye-witness testimonies were manipulated into 3 different categories (credible eye-witness, discredited eye-witness and no eye-witness). Evidence by the prosecution and defence sides were also presented and were consistent across the three independent variable groups. In the past many theorist felt that inconsistencies in eye-witnesses testimonies have been the cause of many wrongful convictions (Neufeld, 2008; Wagstaff et al., 2003). These past beliefs have resulted in the development of this study and the hypothesis that, having any sort of eye-witness present would cause a dramatic influence in generating more guilty verdicts by the participants. However the study results were found to be inconclusive in supporting our hypothesis and possible reasons for this, as well as future studies were discussed.

How Do Eye-witness Testimonials Affect Jury Decision Making?

In a courtroom, jury members are presented with many forms of evidence in order to help manipulate the decision making process. A commonly used form of evidence that is presented by the prosecution side is called an eye-witness testimony. An eye-witness testimony is an observation that a third party had to a crime or incident that took place. The eye-witness will testify as to what they saw and also try to identify who committed the crime.

As stated by Bradfield and Wells (2000), in 1972 in the case of Neil vs Biggers the court declared that for an eye-witness testimony to be valid, 5 criterias had to be met. These were (1) certainty of suspects identification, (2) quality of view the witnesses reports having of the suspect, (3) attention paid to suspect, (4) the degree to which the witnesses description of suspect match that of defendant and (5) time that has elapsed between witnessing crime and identification of suspect. These 5 criteria were later known as the 5 Biggers criteria.

According to Rutledge (2001), eye-witness testimonies in most cases are amongst the most important forms of evidence that is presented. However it must be contrasted that although testimonies are an aid for decision making, there is a wide acceptance that eye-witness evidence is frequently unreliable and inaccurate (Neuschatz et al., 2007; Rutledge, 2001). Scholars have theorised that the acceptances of unreliable testimonies by jury members are largely the result of the high confidence level displayed by eye-witness at correctly identifying the suspect, when in fact they were incorrect (Luss & Wells, 1994; Wells, Ferguson & Lindsay, 1981).

A possible cause to explain how these high confidence levels develop in an eye-witness has been linked to what theorist call the feedback effect. It was shown that feedback comments by police such as, "well done" or "good, you identified him" during interviewing process, had dramatic effects on the eye-witnesses confidence (Luss &Wells, 1994; Wells & Bradfield, 1998).

Koriat, Lichtenstein and Fischhoff (1980, as cited in Wells, Ferguson & Lindsay, 1981), went further and stated that this feedback led to eye-witnesses thinking of reasons that further supported the decision they have made regarding who they identified and the circumstances of the crime they felt they had observed.

Rattner (1988, as cited in Bradfield & Wells, 2000), further states that acceptance of mistaken identification is the largest single cause of wrongful conviction. Rattner's statement was further demonstrated by mock-jury studies undertaken where it was shown that although there were inconsistencies in eye-witness testimonies, the majority of jury members delivered a verdict that the defendant was guilty (Lindsay, Wells & O'Connor, 1989; Wagstaff et al., 2003).

Therefore because of the ever-increasing debate as to the reliability and validity of the statements made and the consequences it has in the jury decision making process, research into eye-witness testimonies is a valuable area of study.

In the study it was hypothesised that firstly, having any sort of eye-witness will incur more guilty verdicts over non guilty verdicts. Secondly, it is hypothesised that with the presentation of a witness, the probability or confidence level that the suspect is guilty should increase over that of having no witness. Therefore the more credible a witness is, the more probability the participants should show of having a guilty verdict.



The study comprised a total of 139 PYB 102 students from Queensland University of Technology. Participants were recruited for this study by means of a consented volunteering process held during a tutorial session. The total number of students comprised of 107 females and 32 males whose age range varied between 17 to 51 years of age. This equates to an average age of 21.8 years and a standard deviation of 7.5 years.


All participants were presented with an identical argument by the prosecution and defence lawyers, however the information regarding the eye-witness testimony were altered for participants to form 3 different points of view regarding the eye-witness testimony. Therefore, the independent variables in this study were the 3 different arguments that were presented regarding eye-witness testimonies (no eye-witness, discredited eye-witness and a credible eye-witness). The 2 dependent variables which were the outcomes of this study were the guilty or not guilty verdicts and the participants probability (confidence level) at the suspect committing the crime.


Participants were given a sheet stating the crime scenario with relevant facts about the crime, suspect, circumstances of the arrest and evidence presented to jury in court. Other materials used in this study were pen and paper questionnaire. The questionnaire required a choice between a guilty or non guilty verdict along with a probability of guilt ranking from 0% to 100%.


Each participant received information regarding a crime scenario. Information given, stated how the crime took place and how the suspect was arrested. Participants were also advised by the prosecution side of the evidence that was found in the suspects' possession or on suspects' hands and shoes. The defence team also presented their side, stating a counter-reason behind the evidence and possessions being claimed by the prosecution side. Participants were also given information regarding eye-witness testimonies.

The information regarding eye-witness testimonies were used as an independent variable in the study and were altered into 3 scenarios which affected the accuracy of the testimonies. Group 1 was presented with information that had no eye-witness statements while group 2 was presented with an eye-witness who had witnessed the crime but was not wearing his glasses at the time and was legally declared blind. Group 3 was presented with an eye-witness who claimed to have seen the incident and had no issues regarding his sight.

After being presented with all the information, participants were asked to do two separate tasks. Task 1 was a categorical task whereby participant had to select whether they felt the suspect was guilty or not guilty. The second task was to numerically state the probability that the suspect was guilty. This confidence level had a possible value which ranged from 0% probability (absolutely not confident that suspect committed the crime) to 100% probability (absolutely confident the crime was committed by suspect).


Table 1 shows the decisions made by participants of guilty vs not guilty, while table 2 shows how probable the participants felt the suspect was guilty based on the eye-witness testimonies they were presented.

Table 1.

Decisions Made by Participants Based on Eye Witness Testimony.

Experimental Condition Guilty Not Guilty

No witness 15 (33%) 30(67%)

Eye-witness 21(45%) 26(55%)

Discredited eye-witness 7(15%) 40(85%)

Table 2.

Probability that Participants Felt Suspect was Guilty Based on Eye-Witness Testimony.

Experimental Probability suspect Standard

Condition Is Guilty Deviation

No witness 45.22 22.36

Eye-witness 50.10 21.93

Discredited eye-witness 36.38 19.24


Results found that the percentage differences in guilty verdicts across all three groups were statistically significant using a chi-square test of independence which concluded that p = 0.007 existed ( x2 (2, N=139) = 9.94). Also the only probability or confidence level that was shown to be significant using independent sample t-test was only apparent between the difference in the eye-witness group and discredited eye-witness group.

It was found that participants had a higher percentage of not guilty votes when presented with either a credible witness or a discredited witness and therefore the first hypothesis has been found to be inconclusive. As stated by Hosch, Beck, and McIntyre (1980), a majority of not guilty verdicts may have been chosen by jurors not because they felt that the defendant was innocent, rather they may have felt the evidence and eye witness testimonies had not proven guilt beyond a reasonable doubt.

The second hypothesis was also found to be inconclusive in that although we expected having an eye-witness (discredited or credible) would have a higher probability or confidence level than having no eye-witness, our results contradicted this by showing that the no eye-witness group had more guilty verdicts than the discredited eye-witness group. However, in partial support of the second hypothesis, it must be noted that having a credible eye-witness did produce a higher probability of guilt than having no eye-witness.

This outcome could be explained by the fact that participants understood the implications of guilty verdicts based on information which do not prove beyond a reasonable doubt. Another point to note is participants have access to internet websites that highlight information regarding suspects who were originally guilty due to evidence such as eye-witness testimonies, but have been exonerated through DNA testing.

As supported on their website by Scheck and Neufeld (2008), eye-witness identification is frequently inaccurate and that eye-witness misidentification is the single greatest cause of wrongful convictions that were overturned through DNA testing.

Another study which supports the second hypothesis is summarised by Kennedy and Haygood (1992), who states the discrediting of an eye-witness will undermine any influence the witness had on the decision making process.

Limitations of this study included factors such as the study was a theoretical case and hadn't truly represented all factors that would be presented in a real courtroom, this included the limited evidence presented. Another point to note is that because of the theoretical example, participants couldn't incorporate true emotions that jurors felt when presented with in-depth evidence in real court situations such as the violent nature of crimes.

Secondly participants with prior exposure to jury exposure may have a different outlook to decision making compared to participants who haven't had previous exposure. These limitations could help devise future studies by comparing studies with only non-exposed jury participants against exposed participants.

In summary, it has been found that this study was inconclusive to determine if the hypothesis could truly be rejected. Therefore it would be advisable to perform further studies in the future in order to further develop a better understanding on how eye-witness testimonials affect jury decision making process.