Also known as:FRE 703 · Fed. R. Evid. 703 · Rule 703
Written by attorneys · grounded in primary & secondary sources — see below
A federal evidentiary rule permitting an expert witness to base an opinion on facts or data made known to the expert even if those facts or data are themselves inadmissible, provided experts in the particular field would reasonably rely on the same kinds of materials.
Sources & Authorities
How it applies
Common Examples
2
Expert Relies on Undisclosed Algorithm
Felix Franco, a software engineer retained by Frontier Capital, formed an opinion that a competitor's chip copied proprietary code. He based the opinion on similarity scores from a proprietary algorithm whose dataset and methodology were never disclosed, plus written summaries prepared by two unidentified junior analysts. The court admitted the testimony under the rule because experts in the field would reasonably rely on such materials even if the underlying data remained inadmissible.
Expert Draws on Medical Literature
Farah Fox sued Baxter Healthcare Corp. after developing atypical connective tissue disease following breast implant surgery. Her expert relied on published epidemiological studies and case reports that would not themselves be admissible to prove causation. The court permitted the opinion because experts in the relevant medical field would reasonably rely on those types of materials when forming conclusions about product-related disease.
What standard determines whether an expert may rely on otherwise inadmissible facts or data?+
The rule permits reliance when experts in the particular field would reasonably rely on the same kinds of materials. The court evaluates whether the materials are of a type customarily used by specialists in forming opinions on the subject.
May an expert base an opinion solely on materials supplied by counsel?+
Yes, provided the materials are of a type reasonably relied upon by experts in the field. The rule does not bar reliance merely because counsel selected or prepared the data.
Does the rule allow an expert to disclose the underlying facts or data to the jury?+
The rule itself addresses the permissibility of the basis. Disclosure to the jury is governed by related provisions such as Rule 705, which permits an expert to state an opinion without first disclosing the underlying facts unless the court orders otherwise or cross-examination requires it.
428 Mass. 1, 696 N.E.2d 909 (1998)Torts
…Servs. v. A Juvenile , 398 Mass. 516, 531 (1986), in which we declined to adopt Proposed Mass. R. Evid. 703 (the equivalent of Fed. R. Evid. 703), and instead took “a modest step by permitting an expert to base an opinion on facts or data not in evidence if the facts or data are independently admissible and are a permissible basis…
EvidencePresentation of evidence · Impeachment, contradiction, and rehabilitationUBEIntermediate