Rule 703

Rule 703 is a Federal Rule of Evidence that lets an expert witness form opinions based on facts or data that the expert reviewed outside the courtroom, even if some of that underlying material would not itself be admissible at trial. The material must be the kind of information experts in that field normally rely on to reach conclusions. The expert can usually share their conclusion with the jury, but generally cannot recite the inadmissible underlying material unless the judge decides the jury needs to hear it to evaluate the opinion.

Origin

Rule 703 was enacted as part of the Federal Rules of Evidence in 1975 and was significantly amended in 2000 to tighten when the underlying inadmissible material can be disclosed to the jury. Most states have adopted parallel versions in their own evidence codes.

Significance in Asbestos Context

This rule is one of the workhorses of asbestos cases because the medical and scientific opinions that prove your case are built on layers of background material, pathology slides, prior medical records, industrial hygiene reports, published epidemiology studies, OSHA documents, and historical product literature. Without Rule 703, your treating physicians and retained experts (pulmonologists, pathologists, industrial hygienists) would not be able to rely on this body of information to explain how your exposures caused your disease. Defendants frequently use Rule 703 the other way, challenging whether your expert truly relied on the type of data experts in that field accept, or arguing that prejudicial background material should be kept from the jury. Expect motions in limine and Daubert-style challenges to focus on what your experts considered and whether they may describe it to the jury.

Example Sentence

Under Rule 703, the plaintiff's pulmonologist was allowed to base his causation opinion on the patient's work history, prior chest CT scans, and peer-reviewed studies on chrysotile exposure, even though some of those documents were not themselves admitted as exhibits.

Related Terms

Expert Witness, Daubert Standard, Federal Rules of Evidence, Causation Opinion, Rule 702, Motion in Limine

Notes

• Give your legal team a complete list of treating doctors, employers, union halls, and military assignments so your experts can rely on a full and accurate record. Gaps in the underlying data are a common target for defense challenges.
• Preserve original medical records, pathology reports, imaging discs, and any work-history documents (W-2s, social security earnings records, union books); these are exactly the kinds of materials experts rely on under Rule 703.
• Ask your attorney whether the defense has filed a motion to exclude or limit your expert's testimony, and whether any Rule 703 issues affect what the jury will be allowed to hear about the basis of your expert's opinion.
• Rule 703 works alongside Rule 702 (Daubert). An opinion can survive Rule 703 but still be excluded under Rule 702 if the methodology is unreliable, so both rules typically come up together.