Cognitive psychologists as expert witnesses

The first part of this paper defines a central problem for professional ethics: whether agents in professional roles are to act on their own moral perceptions or rather defer to those with special authority to make decisions within particular institutional settings. Specifically, should the psychologist decide for himself whether and how to testify as an expert witness, or should he allow the judge and lawyer to settle these questions for him? I argue that he must decide for himself and attempt to control the nature of his testimony. Given this preliminary conclusion, the second part of the paper argues on direct moral grounds first for a general presumption in favor of psychologists' testimony on the accuracy of eyewitnesses. Such testimony fits the legal criterion of reasonable doubt, if the psychologists' information is more accurate than that of the average juror and lawyer. Second, it is argued that the expert witness must resist intense adversarial pressures and present his testimony as impartially and objectively as possible.