Expert testimony refers to information provided during a court case by an individual qualified to testify about a specialized subject area. This type of action is usually used and allowed to assist judges and jurors in understanding subjects that are beyond the common comprehension of an average individual. Although this type of testimony differs from other types, it is subject to certain rules, which may vary from one jurisdiction to another.
Sometimes information is presented in a case that could be pertinent to the decision reached, if it is properly understood. That understanding may require clarification. An expert may be called upon to provide this information.
Many people falsely believe that expert testimony must be provided by individuals qualified by certain titles or degrees. In the United States (US), according to the Federal Rules of Evidence (FRE), an expert can be qualified by their experience or education. Many states have adopted these federal standards or outlined rules that are similar. In the courtroom, however, it is common to find that attorneys will attempt to use credentials to either highlight why expert testimony should be heavily relied upon or why it should be discounted.
Expert testimony often differs from other types of testimony because the witness does not have to provide any factual information about the case. In many instances, the information that such witnesses provide is based on opinion and speculation, which is generally not permissible. The reason that exceptions are made in this regard is because the purpose of expert testimony is often to confirm that a certain set of circumstances is or is not possible. In a vehicular manslaughter case, for example, a mechanical expert may be asked to testify about the likelihood that a particular defect could cause a vehicle to perform a certain way.
Both plaintiffs and defendants generally have the opportunity to introduce relevant expert testimony. The two sides may bring experts with opposing views to the stand. An expert’s claims may be challenged by the opposing side. When this is done, the witness may be asked to provide support for the basis of his conclusions.
Furthermore, there are instances when a court may deem expert testimony to be inadmissible. One example is when an expert speaks on subjects that are common, or which do not require special knowledge. There are generally no set rules to determine this, meaning a topic may be considered common knowledge in one court but may be viewed as a specialized subject in another.