Sobering truths: The influence of victim intoxication status and expert testimony on mock jury decision-making

Objectives: Victims are often intoxicated with alcohol during crimes and jurors must evaluate their testimony at trial. This study investigated the impact of (1) a victim’s intoxication status and (2) expert testimony, on mock jurors’ assessments of victim credibility and verdict decisions in a simulated trial involving group deliberation. Hypotheses: We expected more pro-defence decisions (i.e., lower victim credibility ratings and fewer guilty verdicts) as victim intoxication level increased. We also anticipated more pro-defence decisions when expert testimony was absent compared to present. Finally, we expected the informative effects of expert testimony to be more pronounced at lower levels of victim intoxication. Method: The current study employed a 4 (victim intoxication status: sober, low, moderate, severe) x 2 (expert testimony: present, absent) between-subjects design. Participants (N = 170) listened to a fictional trial and provided individual ratings of victim credibility and verdict decisions. Mock jurors then engaged in deliberation to render group verdicts. Participants’ demographic data and alcohol-related consumption and work/training history were also collected. Results: Intoxicated victims were generally viewed as less credible compared to sober victims. However, mock jurors did not differentiate between specific intoxication levels when assessing credibility. Sensitivity to intoxication level only slightly improved following secondary analyses that clarified mock jurors’ perceptions of the victim’s intoxication status. Both pre-deliberation verdicts and pre- to post-deliberation verdict changes were impacted only when the victim was sober compared to severely intoxicated. Expert testimony did not affect perceptions of victim credibility or verdicts. Conclusions: The dose-dependent relationship between alcohol intoxication and eyewitness memory is not a matter of common knowledge among jurors. Explicit clarification of an individual’s degree of intoxication and what this means for their testimony is essential at trial. Future research should refine expert testimony as a method of evidence-based support for jurors in intoxication-related cases.