Opinion Testimony Law and Legal Definition
Opinion testimony is testimony based on one's belief or idea rather than on direct knowledge of the facts at issue. Generally, unless an express exception exists, opinion testimony is not admissible in court. Opinion testimony from a lay witness or an expert witness may be allowed in evidence under certain conditions.
According to USCS Fed Rules Evid R 702, a qualified expert may testify “in the form of an opinion or otherwise” so long as: “(1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.”
As per USCS Fed Rules Evid R 701 a witness may testify in the form of opinion if the opinion is limited to those opinions or inferences which are (a) rationally based on the perception of the witness, and (b) helpful to a clear understanding of the witness' testimony or the determination of a fact in issue, and (c) not based on scientific, technical, or other specialized knowledge.