Rule 705. Disclosing the Facts or Data Underlying an Expert’s Opinion


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.



2011 Advisory Committee Note. – The language of this rule has been amended as part of the restyling of the Evidence Rules to make them more easily understood and to make style and terminology consistent throughout the rules. These changes are intended to be stylistic only. There is no intent to change any result in any ruling on evidence admissibility. This rule is the federal rule, verbatim.




This rule is the federal rule, verbatim. The substance of this rule was formerly found in Rules 57 and 58, Utah Rules of Evidence (1971). The requirement that an expert disclose the underlying facts or data for his opinion when cross-examined was formerly found in Rule 58, Utah Rules of Evidence (1971). The discretion vested in the trial judge to require prior disclosure of underlying facts or data should be liberally exercised in situations where there has not been adequate discovery in civil cases or disclosure in criminal cases.