Lay Opinion Testimony Law and Legal Definition

Lay opinion testimony refers to evidence given by a witness who is not qualified as an expert but who testifies to opinions or inferences.

USCS Fed Rules Evid R 701 provides that a witness may testify in the form of opinion if the opinion is rationally based on the perception of the witness and helpful in understanding his/her testimony or in determining a fact in issue. Lay witness opinion is admissible so long as it would be helpful to the factfinder and is rationally based on personal perception. This rule recognizes that a lay witness' opinion can more helpful at times than the raw data on which the opinion is based. An opinion is often a convenient shorthand device. For example, testimony that a person was "excited" or "angry" is more evocative and understandable than a long, physical description of the person's outward manifestations.

The relevant law as it appears in the statute:

USCS Fed Rules Evid R 701. Opinion Testimony by Lay Witnesses

If the witness is not testifying as an expert, the witness' testimony in the form of opinions or inferences 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 within the scope of Rule 702.