Rule 701 Federal Rules of Evidence
Rule 701 of the Federal Rules of Evidence is about Opinion Testimony by Lay Witnesses. It is under Article VII (Opinions and Expert Testimony) of the Rules.
If a witness is not testifying as an expert, testimony in the form of an opinion is limited to one that is:
(a) rationally based on the witness’s perception;
(b) helpful to clearly understanding the witness’s testimony or to determining a fact in issue; and
(c) not based on scientific, technical, or other specialized knowledge within the scope of Rule 702.