The article analyses the role of social scientists as expert witnesses in the ICTY, whose contribution is assessed in the light of the long development of this practice. Wider discussion on the courtroom usage of scientific knowledge is evoked in order to emphasize the problems in regulation of expert witnessing. Differing mechanisms set to ensure the scientific reliability and legal relevance of the contribution of experts is analyzed in different legal contexts and in different scholarly disciplines. Regulation of expert witnessing in The Hague tribunal is perceived as specific solution whose consequences are tracked through the role of experts in the trials and through the public perception of this role. The goal of such approach is to nuance the dominant interpretations on the role of scholars in the Hague tribunal and to create the preconditions for understanding of the specific character of their role.