Legal control of expert witness bias

Abstract

Impartiality of expert witnesses means that such experts operate within scientific principles and legal procedures. By doing so, they assist the trier of fact. There are two aspects to the requirements for the impartiality of expert witnesses: the individual perspective and the industry perspective. Each expert witness must follow individual standards, including avoiding irrelevant information affecting his or her opinions; applying reliable methods; employing reasonable analysis; and providing the findings in comprehensive reports (including a precise description of personal background and expert activity). They must also follow industry standards of forensic science regarding objective technical accessible demands, laboratory management and career management. Biased expert witnesses, however, will damage impartiality and impede the goal of assisting the trier of fact. Based on psychological theories such as dual process theory, authoritarian personality and intergroup threat, this paper classifies expert witness bias into four categories: (1) cognitive bias; (2) bias in the analytic process; (3) bias resulting from the position of the expert witness at trial; and (4) the social bias arising from social pressure or economic pressure. Because bias influences the relevance, credibility and impartiality of experts, steps should be taken to restrict certain categories of bias, which can be and must be controlled. Reflecting the differences between the Anglo-American legal system and the Chinese legal system, in China the bias of expert witnesses should be controlled in terms of actions, occupational management and independence of laboratories.