Expert witnesses are now used in most civil and criminal cases. Testimony by such witnesses, or the full or partial exclusion thereof, will often “make or break” a prosecutor’s or plaintiff’s case. Not surprisingly given the stakes involved, debate over the appropriate use of courtroom expert testimony has become one of the most significant controversies in both criminal and civil law. This seminar will address various topics within this broad controversy, such as: why are there special, strict rules for expert testimony? what is the appropriate standard for the admissibility of expert testimony? should admissibility standards distinguish between “scientific” and “non-scientific” expert testimony, and, if so, how? should the system of allowing adversarial parties to choose their own experts be supplemented or replaced by court-appointed experts? is it appropriate for forensic crime laboratories to be affiliated with the prosecution?