Legal Definitions - expert testimony

Definition: Expert testimony is when an expert witness gives their opinion on a technical or scientific subject during a trial or deposition. This opinion is relevant to a lawsuit or criminal case. The Federal Rules of Evidence, Rule 702 sets out the requirements for expert testimony to be admissible.

For example, in a murder trial, a forensic expert may give their opinion on the cause of death based on their examination of the victim's body. This opinion can help the jury understand the evidence and determine the facts of the case.

However, not all expert testimony is admissible. In Kumho Tire Co. v. Carmichael, the Supreme Court affirmed a District Court’s decision not to admit expert testimony on tire marks and treads because there was no indication that other experts in the industry use the expert's particular approach or that tire experts normally make the very fine distinctions necessary to support his conclusions.

Overall, expert testimony is an important part of many trials and can help the jury understand complex technical or scientific subjects.