Expert witness testimony is essential to all legal proceedings that involve technical, medical, professional, or scientific matters. More generally, experts must testify whenever the underlying matters are beyond the common knowledge of lay jurors. As we have written in previous articles, the courts have spent much time and energy determining how to access the proper qualifications for experts. Without an expert, a plaintiff cannot proceed to trial, and a defendant is usually doomed to an adverse jury verdict. Since experts are often a scarce resource that is essential to litigation, many charge substantial fees for their services. If the expert does not do a good job, the party employing the expert will lose the lawsuit as well as be responsible for the expert's fees. This article deals with expert witness malpractice. Should the party hiring the expert be entitled to sue the expert for malpractice? Should the party that the expert testifies against be allowed to sue the expert? Conversely, what are the legal risks of being an expert witness?.