THE ART OF EXPERT WITNESSING
"Who is an expert witness and what does an expert do?"
In this initial chapter, we present a description of the expert witness and basic guidelines for the mental health professional who is called in to provide expert testimony in the courtroom. Several books have been published by those experienced in forensic work, and their many suggestions are summarized here.
The definition of an expert witness is, by law, a well-defined concept, yet it is poorly understood by many. During the "trial of the century," People v. O. J. Simpson, the defense called as a witness, Robert Huizenga, MD, a specialist in internal medicine. Regarding Mr. Simpson's rheumatoid arthritis condition, Dr. Huizenga was asked if he would defer to the opinion of a pre-eminent expert who was a Stanford University professor and author in a standard textbook on rheumatoid arthritis. Dr. Huizenga would not yield, and quipped that there are many definitions of an expert and that he had heard as a Harvard University medical student that an expert was "a bastard from Boston with slides." In a court of law, an expert is defined more precisely.
According to Rule 702 of the Federal Rules of Evidence, an expert is a person who, due to specialized training and experience, may provide testimony to assist the trier of fact in understanding evidence that is beyond the layperson's knowledge, or to determine a fact in issue ( Moore, 1985). Thus, the expert must be knowledgeable with the scientific literature in the area of expertise and have the ability to explain technical information in a clear and comprehendible