Also known as: Rule 703 · FRE 703 · Fed. R. Evid. 703 · Federal Rules of Evidence 703
Written by attorneys · grounded in primary & secondary sources — see below
A rule of evidence permitting an expert witness to base an opinion on facts or data made known to the expert or personally observed. Experts in the particular field may reasonably rely on those kinds of facts or data in forming an opinion even if the facts or data are themselves inadmissible.
Fiona Foster, a forensic toxicologist, offers an opinion that the defendant's blood sample contained a prohibited substance. She formed the opinion after reviewing lab reports prepared by technicians she never met and never observed at work. The court admits the opinion because experts in toxicology routinely rely on such reports even when the underlying data would be inadmissible hearsay.
Frank Fisher, a forensic DNA analyst, testifies that two profiles match. He bases the comparison on a report from an outside laboratory that processed the crime-scene sample. The court permits the opinion because analysts in the field customarily rely on such reports, and the defense can test the opinion through cross-examination.
Select any source to read its text and confirm it supports the definition.
An expert may rely on facts or data made known to the expert or personally observed. The rule permits reliance on materials that experts in the field would reasonably use even if those materials would otherwise be inadmissible.
Supporting sources
The proponent may disclose such facts or data only if their probative value in helping the jury evaluate the opinion substantially outweighs their prejudicial effect.
Supporting sources
The personal-knowledge requirement does not apply to expert testimony under this rule. An expert may therefore base an opinion on information supplied by others that the expert has not personally observed.
Supporting sources
The expert may state the opinion without first disclosing the underlying facts or data, but opposing counsel may require disclosure of those materials on cross-examination.
Supporting sources
…opinion are not introduced for a plausible nonhearsay purpose”). This view is directly contrary to the current version of Rule 703 of the Federal Rules of Evidence, which this Court approved and sent to Congress in 2000. Under that Rule, “basis evidence” that is not admissible for its truth may be disclosed even in a…