DISCLOSING THE FACTS OR DATA

UNDERLYING AN EXPERT’S OPINION (a) Disclosure of underlying facts. Unless the court orders otherwise, an expert may state an opinion—and give the reasons for it—without first testifying to the underlying facts or data. But the expert may be required to disclose those facts or data on cross-examination. (b) Objection. A party may object to an expert witness’s testimony on the ground that the expert lacks a sufficient basis for expressing an opinion. Before the expert gives an opinion, counsel may be allowed to examine the expert about the facts or data underlying the opinion outside of the jury’s presence. If there is evidence sufficient to support a finding that the expert lacks a sufficient basis for the opinion, the opinion is inadmissible, unless the party who called the expert witness first establishes the underlying facts or data.