Social psychologists possess expertise relevant to multiple types of criminal and civil legal cases. At the same time, due to the structure and norms of the adversary system, scholars face challenges to their scientific objectivity and identity as they enter the legal system as experts; further, their participation can generate controversies within their disciplines. This chapter reviews the macro-, meso-, and micro-level contexts of serving as a legal expert, with the aim of identifying the expert’s place within the adversary system, the effect of expert participation on professional standards, and micro-level questions of what makes experts trustworthy.