What happens when two systems, law and medicine, are joined in the arena of the court? This work deals with the structure and the premises of two diverse discourse models; the approach is anthropological. Several chapters are preponderantly based on legal research, addressing cases requiring testimony by expert witnesses on recent technologies used in the laboratories of medical scientists. Descriptions of other societies and cultures consider the identical problems of rights, privileges, and duties, and provide perspectives to cultural self-knowledge. The volume draws on cultural, historical and contemporary examples such as the O.J. Simpson case. It can be used as a text for courses taught in medical schools and law schools.