Juror Decisions Eyewitness Condition LayPolice Police: High Credibility Police: Low CredibilityF Pre-deliberation Witness Trustworthiness 7.17 a (.21) 7.64 a (.21) 7.85 a (.20) 6.06 b (.21) 15.27*** Verdict x Certainty.30 (.43).62 (.44).62 (.41).82 (.42).26 Post Deliberation Witness Trustworthiness 6.32 ab (.22) 6.75 a (.23) 6.93 a (.21) 5.83 b (.22) 5.12** Verdict x Certainty b (.39) a (.40) ab (.37) b (.38) 3.47* Comparing Police Eyewitnesses and Lay Eyewitnesses: The Effect of Eyewitness Credibility on Juror Verdict Decisions Lindsey M. Cole & Ellen S. Cohn Department of Psychology, University of New Hampshire Pre-deliberation Verdict  No significant differences in verdict decisions or verdict/certainty  Slight to moderate inclination towards guilt in all conditions Trust in the Witness  Only police officer witnesses with low credibility were viewed as less trustworthy  All other witness types were not significantly different in level of trustworthiness between conditions Post Deliberation Verdict  Large shift in verdict decisions for police conditions  Particularly pronounced in police (no credibility manipulation) and police high credibility conditions  Majority acquitted the defendant  Police eyewitness resulted in significantly greater certainty for not guilty verdicts than the lay or police with low credibility eyewitness conditions Trust in the Witness  Distinction between police and police with high credibility compared to lay and police with low credibility emerging  Police were viewed as more trustworthy, however the police officer and high credibility police officer eyewitness conditions resulted in the most acquittals Implications and Future Directions  Police were viewed differently than the lay witness  This difference affected perceptions of the witness and verdict decisions  Differences only emerged after group deliberation  Information provided about the police officer is important  Credibility seems to be a factor in distinguishing the police from lay witnesses  Future studies need to examine the acquittal effect of police officer eyewitness testimony Results Method Introduction Participants:  132 university students  62 % female  Age (M = 19.12, SD =1.67) Measures:  Eyewitness trustworthiness  1 (not trustworthy at all) to 10 (very trustworthy)  Verdict decision  Guilty (1), not guilty (-1)  Certainty for verdict  1 (not very certain) to 5 (very certain) Procedure:  Trial video with jury instructions  Convenience store robbery  Four versions  Lay eyewitness or police officer eyewitness  Police officer eyewitness credibility (low, high, neutral)  Pre-deliberation questionnaire  Eyewitness trustworthiness, verdict, and certainty for verdict  Group deliberation  Groups of 6 participants  Post deliberation questionnaire  Eyewitness trustworthiness, verdict, and certainty for verdict References Kassin, S. M., Williams, L. N., & Saunders, C. L. (1990). Dirty tricks of cross-examination: The influence of conjectural evidence on the jury. Law and Human Behavior, 14(4), doi: / BF Tanford, S., & Cox, M. (1988). The effects of impeachment evidence and limiting instructions on individual and group decision making. Law and Human Behavior, 12, 477– 497. Wells, G. L., Lindsay, R. C. L., & Ferguson, T. J. (1979). Accuracy, confidence, and juror perceptions in eyewitness identifications. Journal of Applied Psychology, 64, Yarmey, A. D. (1986). Perceived expertness and credibility of police officer as eyewitnesses. Canadian Police College Journal, 10(1), For more information: Χ 2 (3) = 1.06 Χ 2 (3) = 13.71** Discussion  Witness testimony is one of most influential factors in juror decisions (Wells et al., 1979)  The majority of researchers have focused on lay eyewitnesses or expert witnesses (Kassin et al., 1990; Wells et al., 1979)  Few researchers have examined police officers as witnesses despite the unique role they have in the courtroom (Yarmey, 1986)  Police may be viewed as legal experts even when testifying in an eyewitness capacity  Previous researchers have yet to compare the effect of lay eyewitnesses with police officers as eyewitnesses  Juror perceptions of credibility and trust in the witness are important in juror verdict decisions  Witnesses who have low credibility have been shown to produce more not guilty verdicts when testifying for the prosecution than witnesses with high credibility (Kassin et al., 1990; Tanford & Cox, 1988).  Jurors may find the credibility and trustworthiness of a lay eyewitness to be different from that of a police officer eyewitness  The purpose of the current study was to determine if juror perceptions of eyewitness trustworthiness and verdict decisions differed pre-deliberation and post deliberation when presented with one of four eyewitness conditions:  Lay eyewitness or police officer eyewitness (high credibility, low credibility, or neutral) Note: The letters refer to the results of Tukey HSD post hoc tests. a is the largest mean, b is the smallest mean. *p<.05, ** p<.01; *** p<.001