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Expert Witness Hearsay: What is Admissible?

Hearsay, or an out of court statement submitted to prove the truth of what it asserts, is one of the most complex evidentiary categories.

Dani Alexis Ryskamp, J.D.

Written by
— Updated on April 27, 2022

Expert Witness Hearsay: What is Admissible?


While hearsay is generally inadmissible as evidence, a number of exclusions and exceptions allow statements that meet the definition of hearsay to be presented in court.

Expert witnesses frequently rely on the work of other experts to inform their opinions. The relied-upon professionals may not be present in court; in some instances, they may no longer even be alive. To what extent is an expert witness’s basis for an opinion admissible, and to what extent is it hearsay?

While various state courts differ as to the details of this question, some general guidelines can help attorneys begin to explore questions of hearsay in expert witness testimony.

Understanding Hearsay in the Expert Witness Context

Federal Rule of Evidence 703 allows an expert witness to “base an opinion on facts or data in the case that the expert has been made aware of or personally observed.”

Rule 703 goes on to explain that if the facts or data are the type that experts in the same field would reasonably rely on to form similar opinions, the facts or data do not have to be admissible in order for the witness’s opinion to be admissible. However, inadmissible facts or data may be disclosed to the jury “only if their probative value in helping the jury evaluate the opinion substantially outweighs their prejudicial effect.”

Rule 703 raises several issues worth considering when evaluating expert witness testimony for hearsay.

Reliability of Third-Party Information

Determining whether the third party information is the type of information experts in the field “would reasonably rely on” is the responsibility of the trial judge. An attorney seeking to qualify a witness’s testimony, then, should prepare to argue that the information relied upon is the sort that experts in the field typically use.

It is also wise to consider arguments that the information itself is reliable. Some courts have interpreted Rule 703 to mean that the information itself should have an independent, objective value beyond its use in the particular case. Arguments that the underlying information is a fundamental part of education in the field, or that it underlies or advances key understandings in the field, can help demonstrate its reliability.

Prejudice and Hearsay

Rule 703 seeks to balance the value of expert witness testimony with concerns about hearsay by allowing an expert to testify as to the opinion they formed based on underlying information without disclosing the underlying information used. The concern is that juries will hear the facts or data the expert used and assume that those facts or data are true — no matter how closely they are cautioned to remember that the facts or data are submitted only to show what the expert thinks or believes.

Underlying information that is otherwise inadmissible cannot be admitted under Rule 703 without a judge’s determination that it will do more to help the jury evaluate the expert than to prejudice the case.

One place to consider drawing the line is at reliance vs. repetition. An expert stating that he or she relied on outside information (without disclosing it) is generally more likely to be admissible than an expert repeating that information in his or her testimony.

Expert Witness Reports and Hearsay

As in other forms of professional writing, expert witness reports should cite their sources. They should acknowledge that the expert consulted other sources and identify the role of those sources in the formation of the expert’s opinion. Acknowledging and identifying sources fulfills the goal of “reliance,” disclosing the points at which the expert turned to sources typically used in his or her field.

Expert witness reports that quote, summarize or paraphrase these sources, however, run the risk of crossing into “reporting” territory, which can cause them to run afoul of Rule 703’s safeguard against prejudice.

For example, an expert witness report might state “Based on my analysis above, I concluded that a breach of duty occurred. After reaching this conclusion and before preparing the final draft of this report, I consulted three other experts in the field.”

This example discloses that the expert relied on other sources, but it does not repeat the opinions of those sources. When presented in court, this example can bolster the expert’s reputation and reliability without introducing information (the out of court statements of the three consulted experts) that jurors might improperly believe to be true.

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