Expert Testimony Definition and Legal Meaning

On this page, you'll find the legal definition and meaning of Expert Testimony, written in plain English, along with examples of how it is used.

What is Expert Testimony?

n. A specialist’s opinions that are stated during a trial or deposition. The specialist is qualified as an expert on a subject that is relevant to the lawsuit or criminal case.

History and Meaning of Expert Testimony

Expert testimony is a crucial part of legal proceedings that requires specialized knowledge and/or skill. An expert witness can be a professional such as a doctor, engineer, or accountant who is called to testify in court, or to write a report, on a subject that is beyond the knowledge or understanding of the average person. The idea of expert testimony dates back to medieval times and was used in the European courts. In the United States, the use of expert witnesses evolved over time and was eventually defined and regulated by the Federal Rules of Evidence.

Expert testimony is allowed in civil and criminal cases to provide the court with opinions or interpretations relating to factual evidence. The expert witness must follow certain ethical standards when giving their opinion and must be truthful and unbiased, with their expertise clearly supported by their qualifications and experience.

Examples of Expert Testimony

  1. In a medical malpractice case, a doctor can provide expert testimony to explain how the defendant's actions were a deviation from the standard of care and caused harm to the plaintiff.
  2. In a corporate fraud case, an accountant can provide expert testimony to explain complex financial transactions and how they were manipulated to deceive investors or management.
  3. In a patent infringement case, a scientist or engineer can provide expert testimony to explain how the defendant's product infringes on the plaintiff's patent.

Legal Terms Similar to Expert Testimony

  1. Lay testimony: statements given by a witness who does not have specialized knowledge or expertise.
  2. Hearsay: information that is repeated by a witness who did not witness the event firsthand.
  3. Judicial notice: a fact that is accepted as true without requiring proof.