365 Expert Witness & Credibility

Research by Cramer, Robert. J., Brodsky, Stanely. L., DeCoster, Jamie., (2009).

Written by Shannon Cantalupo, B.S. 

How do jurors assess an individual’s credibility? What makes them believe one person more?

Researchers were interested in what factors could impact perceived credibility of male expert witnesses. They assessed whether the expert witness’ confidence and the personality characteristics of the jurors affected the credibility of the expert witness and how this influenced jurors’ sentencing recommendations.

Three hundred undergraduates in three groups watched a scripted video with an expert witness showing either low, medium or high confidence. Each participant rated the expert witness’ credibility and completed a personality measure. Acting as a juror, they gave recommendations for sentencing.

Results? Participants gave higher credibility ratings to expert witnesses who showed a medium level (versus low or high) of confidence. “Juror” participants scoring high on extroversion were more likely to see an expert witness as credible. Lastly, expert witness credibility did influence the sentencing outcomes of the jurors, as those who viewed the highest credible witnesses (“for the prosecution”) assigned harsher sentences.

What are the implications? The most effective witness may not be the supremely confident witness. The extroversion in jurists makes a difference in judging witnesses. These factors may influence jury selection and witness preparation.


Cramer, R. J., Brodsky, S. L., DeCoster, J., (2009). Expert witness confidence and juror personality: Their impact on credibility and persuasion in the courtroom. The Journal of American Academy of Psychiatry and the Law, 37(1), 63-74.

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