This paper investigates relationships between several courtroom variables, including expert witness confidence, juror personality, expert witness credibilty and juror sentencing. It finds expert witness confidence to have a significant effect on ratings of credibility, with moderate levels of manipulated confidence yielding the highest credibility. In the study, juror extroversion was positively related to perceptions of expert witness credibility. Predictably, juror ratings of expert witness credibility predicted juror sentencing outcome.