Appeal to Expert Testimony – A Bayesian Approach

Abstract

In this chapter, we offer a Bayesian model for evaluating expert testimony in the court room. Statements from a putative expert are difficult for a legal decision maker to assess, as the legal decision maker – who lacks expert knowledge on the subject issue – must distinguish between experts that are highly reliable and experts that are less reliable. A methodology for the assessment of the expert testimony has been suggested previously, in the works of Walton and Goldman, and we develop this methodology further, using a Bayesian approach to reliability assessment. The reliability of an expert can be questioned on different grounds (lack of competence, bias and lack of motivation), and we clarify different effects that these grounds can have on the expert’s reliability.