Expert Reliance on Inadmissible Information Permitted—Rule 703
Rule 703 expressly permits an expert to base an opinion on facts or data “perceived by or made known to the expert at or before the hearing.” If the facts or data are “of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence in order for the opinion or inference to be admitted.” Fed. R. Evid. 703 (emphasis added). Under Rule 703, experts may opine based on inadmissible information so long as others in the field reasonably rely on the same type of information in performing their jobs out of court.
Admitting the Expert’s Opinion—Rule 702
Rule 703 is not the end of the story. To be admitted, the expert’s opinion itself must satisfy the strictures of Rule 702. Rule 702 allows for the admission of expert opinion testimony only if “(1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness applied the principles and methods reliably to the facts of the case.” Fed. R. Evid. 702.
The 2000 Advisory Committee Note makes clear that while Rule 703 allows experts to rely on inadmissible information, the test for admissibility of the opinion itself is governed by Rule 702, including Rule 702(1)’s mandate that the expert’s testimony be based on sufficient facts or data.
There has been some confusion over the relationship between Rules 702 and 703. The  amendment makes clear that the sufficiency of the basis of an expert’s testimony is to be decided under Rule 702. Rule 702 sets forth the overarching requirement of reliability, and an analysis of the sufficiency of the expert’s basis cannot be divorced from the ultimate reliability of the expert’s opinion. . . . When an expert relies on inadmissible information, Rule 703 requires the trial court to determine whether that information is of a type reasonably relied on by other experts in the field. If so, the expert can rely on the information in reaching an opinion. However, the question whether the expert is relying on a sufficient basis of information—whether admissible information or not—is governed by the requirements of Rule 702.
Under the Advisory Committee’s formulation, however, the term sufficient in Rule 702(1) “calls for a quantitative rather than qualitative analysis.” An expert’s opinion will therefore have a sufficient basis under Rule 702 so long as it is supported by a sufficient quantity of inadmissible information—of a type reasonably relied on by other experts within Rule 703—and will be admitted if the overall opinion meets the general reliability standards of Rule 702 and Daubert.
Disclosing the Inadmissible Material to the Jury—Rule 703
Just because the expert’s opinionmay be admissible, however, does not mean that the otherwise inadmissible underlying informationthat the expert relied on can be disclosed to the jury. This could lead to a strange situation where the expert gives an opinion but cannot disclose the basis for that opinion to the jury, leaving the jurors scratching their heads.
Rule 703 has a mechanism to deal with this. It provides that “[f]acts or data that are otherwise inadmissible shall not be disclosed to the jury by the proponent of the opinion or inference unless the court determines that their probative value in assisting the jury to evaluate the expert’s opinion substantially outweighs their prejudicial effect.” This “reverse balancing test” can be used to good effect by allowing—but not requiring—disclosure of the otherwise inadmissible basis to the jury where needed for the opinion to make sense. Courts using this tool will pay careful attention to the danger that the proponent is really trying to “back door” inadmissible evidence at trial through their expert. The ultimate outcome will play out in the balancing required by the rule at a Rule 104 hearing.
Cross Examination—Rule 705
There may be situations where the proponent of the expert, for some tactical reason, tries to get the expert’s opinion in without any of the (inadmissible) factual basis for it. Rule 705 allows this, but in this circumstance the rule also allows the cross-examiner to dig in to the factual predicate. See Fed. R. Evid. 705 (“The expert may testify in terms of opinion or inference and give reasons therefore without first testifying to the underlying facts or data, unless the court requires otherwise. The expert may in any event be required to disclose the underlying facts or data on cross-examination.”). Tactical considerations come into play when cross-examining under Rule 705, since opening the door can result in disclosure of a flood of inadmissible information that would be otherwise unknown to the jurors.
Keywords: Federal Rules of Evidence, 702, 203, 705, Advisory Committee, expert opinion, inadmissable evidence