- Rule 702 allows witnesses who are not directly related to the action or incident in question who are competent because of "knowledge, skill, experience, training or education" to have an opinion concerning the facts.
- Expert witnesses are often called to give testimony in personal injury or other civil or criminal cases where technical, scientific or other specialized judgment will help establish facts.
- Expert witnesses establish nature, scale and specifics of a wide range of facts including damage estimates, blood alcohol levels and psychological mindsets.
- The witness must prove his qualifications and experience to the judge before he will be allowed to testify.
- The witness must offer pertinent testimony that relates in a direct way to the issue in the case: The judge decides whether the expert's testimony is relevant.
- Rule 702 has been re-interpreted several times. As of 2009, the most recent Supreme Court case relating to expert testimony was Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).
