Discuss the role of expert witnesses and the limitations placed on them by court rulings

Answer:

There are three ways in which the law assumes that mental disorders may affect an individual's ability to exercise his or her rights and responsibilities: (1) Defendants who are not guilty by reason of insanity are not criminally responsible for their actions; (2) Defendants who are incompetent to stand trial are unable to exercise their right to participate in their own defense; and (3) mental illness may be a mitigating factor that can lead to a less harsh sentence, or a harsher one. Since neither judges nor juries have expert psychological knowledge that allows them to make these decisions, mental health experts testify about these matters. One conflict between mental health and the law concerns the role of expert witnesses, specialists allowed to testify about matters of opinion (not just fact) that lie within their area of expertise. In Daubert v.Merrell Dow Pharmaceuticals (1993), the U.S. Supreme Court ruled that expert opinion must be based on an "... inference or assertion . . . derived by the scientific method," and courts must determine "whether the reasoning or methodology underlying the testimony is scientifically valid and ... whether that reasoning or methodology can be applied to the facts in issue." Since experts can and do interpret the same information in different ways, and lawyers "shop" for friendly experts who have a history of interpreting evidence in a way that will help their case. Lawyers expect challenges to their expert witnesses' testimony, and they anticipate that experts for the opposing side will present conflicting testimony. One way to limit conflict, and hopefully improve expert testimony, is for courts to appoint neutral experts rather than having each side employ its own "hired gun."