1. 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 -0.73 b (.39) -2.17 a (.40) -1.44 ab (.37) -0.59 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), 373-384. doi:10.1007/ BF01068162 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, 440-448. Yarmey, A. D. (1986). Perceived expertness and credibility of police officer as eyewitnesses. Canadian Police College Journal, 10(1), 31-51. For more information: lindsey.cole@unh.edu 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