The purpose of this document is to assess two questions that have a positive and normative nature respectively: 1) What incentives does the legal and institutional framework of the European Community (EC) and the United States (Federal level) provide to the different agents involved in antitrust proceedings in regards to the use of expert economic testimonies? 2) What legal and social norms could provide appropriate incentives to the different agents involved in antitrust proceedings in order to align the use of expert economic testimonies with antitrust enforcement goals? The research questions are assessed from a comparative law and economics approach. The law and economics approach is based upon the Asymmetric Information Theory and Principal-Agent Theory. The document contains five conclusions that may be summarized in the following statement: regarding expert economic testimonies, an antitrust enforcement system must aim at the minimization of its costs through the mitigation of the consequences of asymmetric information between the adjudicator and the expert. A cost-benefit analysis of the use of expert witnesses must take into account the incentives produced by the interaction among the different regulatory and non-regulatory features of the antitrust enforcement system.
