RULE OF EVIDENCE 703 — Problem Child of Article VII

With the exception of a few evidence scholars, Federal Rule of Evidence 703 is ignored or misunderstood in practice.  There was a time when virtually every motion to exclude an expert witness’s opinion was framed on Rule 703 concepts, either alone, or in conjunction with Rule 702 requirements.  The Supreme Court’s decision in Daubert changed practice by holding that Rule 702 required gatekeeping, and by generally slighting Rule 703.

I.  Reform of the Common Law

Federal Rule of Evidence 703 formally abandoned the common-law requirement that expert witnesses base their opinions upon evidence of record, either personal observations or facts admitted into evidence.  The first sentence of Rule 703, which has remained unchanged since its original adoption, makes clear that an expert witness may rely upon facts or data that are never admitted into evidence.  This sentence details three methods of putting “facts or data” before expert witnesses.  First, expert witnesses may themselves be percipient witnesses to the facts or data upon which they rely.  Second, expert witnesses may learn of facts or data at the trial by observing other witnesses testify or by being asked to assume facts or data for purposes of giving an opinion.  Third, expert witnesses may come to learn of “facts or data” before the hearing.  It is this third method that represents a departure from the common law, and which raises the issue whether the expert witness has relied upon facts or data, which are themselves inadmissible.

The rationale for Rule 703 was the recognition that much of the expert witness’s understanding of an area of science, medicine, or technology was governed by training, prior experience, professional collaborations, and extensive reading, all of which represented the basis, often in large part, of the case-specific opinions that are then offered in the courtroom.  These bases are mostly hearsay, and mostly inadmissible if expert witnesses were to try to articulate any particular aspect of their personal learning.  The rationale for Rule 703, however, also included the economy and convenience of presenting expert testimony without the need of formal proof of predicate “facts or data,” at least if those facts or data were of the type reasonably relied upon by experts in the relevant field.  Not surprisingly, advocates responded by using Rule 703 to inject all manner of hearsay into their trials, including opinion testimony from witnesses that would never testify at trial.  Courts and commentators responded with confusion over whether Rule 703 created a new exception to the rule against hearsay.

II.  Conduit for Inadmissible Evidence

Much academic, judicial, and professional criticism of Rule 703, before its amendment in 2000, centered on the mischief created by expert witnesses’ reliance upon inadmissible evidence and the disclosure of this information to the jury.  To be sure, Federal Rule 705 made clear that the expert witness need not disclose any basis; the expert opinion could be elicited as a conclusory opinion, or the expert could disclose some but not all bases.  Parties, however, were often intent to use Rule 703 to present, at least selectively, those relied upon facts and data (and sometimes opinions) that would aid their case, regardless of the admissibility of the disclosed expert witness bases.  If the other side were foolish enough to request a limiting instruction, the proponent would revel in the emphasis that the Court gave to their inadmissible facts and data.[i]

Of course, the presentation of expert opinion without requiring disclosure of bases is hardly calculated to permit jurors or trial judges to assess the validity or correctness of the opinions that they must weigh at trial.  Furthermore, Rule 703 shifted the burden to opposing counsel to elicit bases in order to show flaws or weaknesses in reasoning and inference.  This crossexamination frequently could not take place without eliciting inadmissible evidence.

In 2000, Rule 703 was amended to include its third, last sentence, which creates a presumption against disclosure of inadmissible facts or data to the jury.  The presumption against disclosure may be overcome by a judicial finding that the probative value in helping the jury evaluate the opinion is outweighed by the prejudice of injecting inadmissible evidence into the trial.  Nothing in the revised rule makes the inadmissible “facts or data” admissible, although at one point, the Advisory Committee Notes confuse admissibility and disclosure when it writes in terms of relied upon information that is “admissible only for the purpose of assisting the jury in evaluating an expert’s opinion.”  Such evidence is not admissible at all, which is exactly why the presumption is against disclosure and the alternative is disclosure, along with consideration of a limiting instruction.

III.  Expert Witness Opinions – Castles in the Air

Whether underlying facts are disclosed or not, Rule 703, as currently applied in federal courts, raises serious concerns about whether expert witness opinion testimony has a reliable foundation.  The law in most states is that an expert witness’s opinion can rise no higher than the facts upon which the opinion is based.  If the jury does not hear the bases of the opinion, it cannot meaningfully evaluate the opinion.  Furthermore, the jury cannot make sense of an expert witness’s opinion, when it is bound by a limiting instruction, which explains that it may consider the basis in evaluating the expert witness’s opinion, but it may not consider the basis as evidence that has been established in the case. If this basis is not otherwise established in the case, then the jury would be compelled to reject the testimony as unsupported by facts or data in the case.  If the jury must consider the opinion because the expert witness claims to have relied reasonably upon inadmissible “facts or data,” then the expert witness has been given important fact-finding power in the case.

Perhaps Rule 702, with its imposition of gatekeeping responsibilities upon the trial court, is supposed to solve this problem.  Many of the Circuits appear to be moving toward a requirement of pretrial hearings for Rule 702 challenges, at least when requested, and sometimes even when not.  In some instances, the lack of a proper factual predicate, or unreasonableness in reliance upon an inadmissible factual predicate, can be developed in a pretrial hearing that allows the parties to join issue over the reasonableness of reliance and proof of the predicate facts or data.

IV.  Who Decides Reasonable Reliance?

Some of the earlier case law suggested that the expert witness could validate his or her own reliance upon “facts or data,” as “reasonable.”[ii] Judges, like most people, glibly assumed that what people normally or customarily do is reasonable.  Extending this assumption to the law of expert witnesses, courts have equated the reasonable reliance of Rule 703 with what experts customarily do in their field.[iii] Other courts appeared to go further, especially in the context of forensic expert witness opinion, to equate reasonable reliance with what experts do in their courtroom testimony.

The current view, influenced no doubt by the Supreme Court’s holdings in Daubert, Joiner, and Kumho Tire, has settled on requiring the trial court to make an independent assessment, based upon a factual showing, that the “facts or data” in question may be reasonably relied upon by experts in the relevant field.[iv] One of the important implications of this shift is that courts may now accept an expert witness’s testimony about what he normally does, but if opposing counsel challenges the reasonableness of the practice, with affidavits, testimony, learned treatises, and the like, then the court will be required to make a preliminary determination of the reasonableness of the expert’s “normal practice.”  Given that litigation often involves unusual situations outside both the statistical and prescriptive “norms” of ordinary life, the abandonment of extreme deference to expert witnesses as the ultimate arbiters of reasonableness is a significant advance in the evolution of the Federal Rules of Evidence.

V.  Reasonable Reliance and Reliability:  The Intersection Between Rules 702 and 703

Some of the early enthusiasm for Rule 703 as a speed bump for unreliable expert witness testimony came from the explicit use of the concept of “reasonable reliance” in the second sentence of the Rule.  The original Advisory Committee Note encouraged this view by giving an example, without much analysis, of an accident reconstruction expert whose testimony would not be reasonably based upon the statements of bystanders.  Before the advent of Daubert, this example was a tease to lawyers who were looking for some way to limit the flood of unreliable expert witness opinion testimony.  The Advisors, however, did not explain why such reliance would be unreasonable.  We could certainly imagine situations in which bystanders’ statements were essential to recreating an accident.  Furthermore, the statements of bystanders might be admissible under various exceptions to the rule against hearsay, and the Note thus seems to contradict the actual language of the Rule, which limits the reasonableness requirement to reliance upon inadmissible evidence.  In any event, the Advisory Committee’s example of an “accidentologist” seemed to imply a requirement of trustworthiness, which might apply to both admissible and inadmissible “facts or data.”

Perhaps because of the original Advisory Committee Note, litigants, in challenging the reliability of expert witness opinion testimony, frequently invoked both Rules 702 and 703 in support of exclusion.  Indeed, cases that focus on only Rule 703 are relatively uncommon; most cases note that they are addressing motions to bar expert witnesses, made under both rules.  After the Supreme Court’s Quartet on Rule 702 (Daubert, Joiner, Kumho, and Weisgram), the need to frame an exclusionary motion on Rule 703 has been largely dispelled.

One case that gave rise to much of the enthusiasm for Rule 703 as a basis for expert witness preclusion was Judge Weinstein’s decision in In re Agent Orange.[v] Some of the expert witnesses in the Agent Orange litigation relied upon checklists of symptoms prepared by the litigants.  Invoking Rule 703 to support exclusion of the expert witnesses’ opinions, the trial court observed that “no reputable physician relies on hearsay checklists by litigants to reach a conclusion with respect to the cause of their affliction.”[vi]

The lesson of Agent Orange was that Rule 703 could serve as a basis for excluding expert witness testimony.  If the expert witness relied unreasonably upon “facts or data,” then that expert witness’s testimony was fatally flawed under the Rules and had to be excluded.  The Court in Agent Orange avoided the obvious conclusion that an expert witness’s opinion, which was not reasonably based upon “facts or data,” could not be helpful to the trier of fact, and thus the opinion would necessarily offend Rule 702, as well.

Practitioners, faced with dubious expert witness opinion testimony after Agent Orange, increasingly relied upon Rule 703, along with Rules 702 and 403, in stating their challenges to proffered opinions.  Many Courts, in ruling upon these challenges, did not separate out their holdings or reasoning, in applying Rules 702 and 703 to exclude opinions.[vii] Some courts, especially before the Supreme Court’s decision in Daubert, framed reliability challenges almost exclusively in terms of compliance with Rule 703.[viii]

The early enthusiasm for an expansive role for Rule 703 as a tool for broad gatekeeping was problematic from the beginning.  Rule 703 has always required “reasonableness” for an expert witness’s reliance upon inadmissible “facts or data.”  The Rule is, and has always been, silent about reliance upon admissible “facts or data.”  As a result, Rule 703 could never have aspired to the principal role of limiting the flow of unreliable expert testimony.  The Rules of Evidence provide ample bases for expert witnesses to formulate unreliable opinions based solely, and unreasonably, upon admissible “facts or data,” such as inadvertent and false party admissions, self-serving statements made to examining physicians, or vanity press publications elevated to “learned treatise” status.  The resulting opinions have little or no epistemic warrant or claim to reliable methodology, but they may readily pass muster under Rule 703.  Furthermore, even if Rule 703 were applied to eliminate all unreasonable reliance upon “facts or data,” the Rule would not have guarded against unreliability that crept into the opinions as a result of invalid inferences or reasoning from “facts or data,” which themselves were beyond reproach.

The Advisory Committee Note to Rule 702, from 2000, attempts to answer some of the questions about the proper scope of Rule 703:

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. In contrast, the ”reasonable reliance” requirement of Rule 703 is a relatively narrow inquiry. 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.

This Note leaves a large gap in the analysis of expert witness opinion evidence.  The question of the sufficiency of an expert’s bases is understandably different from whether the “facts or data” are themselves reasonably (and thus presumably also reliably) relied upon by experts in the field.  Rule 702 provides guidance about the sufficiency of “facts or data,” as well the reliable application of reliable principles and methods to the facts of the case.  Rule 702, however, is silent about the reliability of the starting point in the scientific or technical knowledge:  the data.  Perhaps the Advisory Committee meant to imply that reliable methodology requires obtaining “facts or data” in a reliable way, but it failed to address the issue in the recent amendments to Rule 702.

There is another problem that amended Rules 702 and 703, along with the Advisory Notes, fail to address.  This problem further illustrates the gap in the coverage of the rules, and perhaps it explains why courts have strained at times to include Rule 703 as part of their analysis of the reliability of expert witness opinion testimony.  Consider what happens when a proffered expert witness’s opinion has already been held to satisfy the relevance and reliability requirements of Rule 702.  The Court has explicitly ruled that the expert’s opinion has a sufficient factual basis, and that the expert has reached the opinion by reliably applying reliable methods to the facts of a case.  After the Court’s Rule 702 ruling, the expert witness amends her report to add reliance upon a new study.  The study is unfinished, and unpublished.  The paper has yet to be peer-reviewed.  Furthermore, the study is written in a foreign language, and the expert has relied upon a translation that appears to have errors, with analyses that are at least partially incoherent or incorrect.  This new study no longer raises questions about sufficiency of data, and the expert’s overall opinion, ex hypothesi, satisfies Rule 702.  This new study appears to raise fresh questions under Rule 703, not provided for in the Advisory Committee’s allocation of issues between Rules 702 and 703.[ix] Some courts might think that the addition of another study, even if the study were scientifically questionable, in support of an already 702-sufficient opinion could not be harmful error.  Yet, the additional study would give the jury the sense that the expert witness had a surfeit of support for his opinion.  Furthermore, the additional study would prejudice the adverse party by requiring more cross-examination on details that may test the patience of the factfinder.

VI.  “Facts or Data” versus “Opinions”

Rule 703 describes the condition for permitting expert witnesses to rely upon inadmissible “facts or data.”  The Rule is silent about reliance upon others’ opinions.  Of course, the distinction between facts (or data) and opinions may occasionally be blurred or difficult to discern, but the entirety of Article VII is predicated upon the existence of the distinction.[x] The conspicuous absence of “opinions” from the Rule’s conditional allowance of expert testimony based upon inadmissible “facts or data” would seem to mean that such reliance upon extra-record opinion was not authorized under Rule 703.[xi] Other courts, especially the Third Circuit, have given their blessing to the wholesale backdoor introduction of opinions, and they have not distinguished facts or data from opinions, as the potentially reasonably relied upon inadmissible evidence under Rule 703.[xii] `

The Advisory Committee Note to the 2000 amendment to Rule 702 purports to answer the question of the scope of “facts or data” under Rule 703:

The term ”data” is intended to encompass the reliable opinions of other experts. See the original Advisory Committee Note to Rule 703. The language ”facts or data” is broad enough to allow an expert to rely on hypothetical facts that are supported by the evidence.


The original Advisory Committee Note to Rule 703, however, refers to opinions as within the scope of “facts or data” in just one single passage, and in a relatively narrow context:

Thus a physician in his own practice bases his diagnosis on information from numerous sources and of considerable variety, including statements by patients and relatives, reports and opinions from nurses, technicians and other doctors, hospital records, and X rays.  Most of them are admissible in evidence, but only with the expenditure of substantial time in producing and examining various authenticating witnesses. The physician makes life-and-death decisions in reliance upon them. His validation, expertly performed and subject to cross-examination, ought to suffice for judicial purposes. Rheingold, supra, at 531; McCormick § 15. A similar provision is California Evidence Code § 801(b).[xiii]

The original Note to Rule 703 is highly misleading because opinions that are recorded in medical records would be admissible in any event as business records.  Furthermore, even if physicians must sometimes make life-or-death decisions on the basis of limited, incomplete, undocumented opinions offered by another medical care provider, that in extremis scenario is hardly a propitious basis for opinion testimony at a judicial hearing where the trier of fact is charged with making a deliberate evaluation of the evidence.  Courts and juries are charged with trying to ascertain the truth, and they do not have a warrant to abridge the fact-finding process because a physician, or any other “expert,” at time past was acting under exigent circumstances.

This more recent attempt to endorse Rule 703 as a conduit for other expert “opinions” should fail for several reasons.  First, the entire Article VII concerns itself with opinions and opinion testimony.  To suggest that Rule 703 used “facts or data” to include “opinions” ignores the context of Article VII and the limited exception that Rule 703 was making to common-law procedure.  Second, the original Advisory Committee note spoke only, in one sentence, to opinions of medical-care providers.  These opinions would normally be recorded in the patient’s medical charts and records, and they would be admissible in any event.[xiv] There is nothing in the notes to Rule 703 to support the wholesale inclusion of hearsay opinion testimony.  Third, the expansion of Rule 703 to include opinions should not circumvent the reliability requirements of Rule 702.  Fourth, the rationale of convenience used to support the expansion of the common law through Rule 703 is stood on its head by this expansion to include opinions.  The Rule puts a heavy burden to ferret out reliance upon opinions of other non-testifying experts, and to take adequate discovery of those persons or organizations. This is a heavy price to pay for the “convenience” of having an opinion introduced without the usual safeguards of critical examination of the qualifications of the expert, or the reliability of his opinion.

Until this extension of Rule 703 is checked, practitioners must inquire of their adversary’s expert witnesses, either in interrogatories or in depositions, whether the witnesses have consulted with and relied upon the writings or oral discussions with any other person regarded by the testifying expert witness as an expert.  If the testifying expert witness has relied upon these non-testifying expert’s statements or opinions, opposing counsel may have to entertain the expensive, inconvenient resort to additional discovery of the out-of-court declarant.

VII.  Fulsome Importation of Untrustworthy Opinions Through Rule 703

One prevalent and problematic practice is for expert witnesses to rely upon a study in order to pass through the study’s authors’ conclusions. Most published studies have a basic ordered structure (IMRAD) :

  • Introduction – identifies the purpose and scientific context of the study;
  • Methods – identifies the materials used, the identification, organization, collection of data and controls;
  • Results – reports the data obtained and any statistical analyses of the data; and
  • Discussion – reports the study authors’ interpretation of the results and how they fit within the larger array of data from other studies.

See Luciana B. Sollaci & Mauricio G. Pereira, “The introduction, methods, results, and discussion (IMRAD) structure: a fifty-year survey,” 92 J. Med. Libr. Ass’n 364 (2004).

What becomes clear is that the testifying expert witnesses needs to have access to the methods and the results of published (and unpublished) papers in order to formulate and express their own opinions.  The introduction and discussion sections of relied upon papers are the scholarship and opinions of hearsay declarants, who in modern day publications are often quite untrustworthy.  The first and last section of most articles would rarely satisfy the procedural requirements of Federal Rule of Civil Procedure 26; nor would they satisfy the evidential reliability requirements of Rule 702. Rule 703’s limitation to “facts and data” should exclude the flood of hearsay opinion from relied upon studies by forcing expert witnesses to rely upon what is really necessary to their opinions.  If the testifying expert witness cannot testify without the scholarship and opinions of the relied upon studies, then he is probably not sufficiently expert to be giving an opinion in court.

There are many clear statements in the medical literature, which caution the consumers of medical studies against misleading claims.  Several years ago, the British Medical Journal published a paper by Montori, et al., “Users’ guide to detecting misleading claims in clinical research reports,” 329 Br. Med. J. 1093 (2004).  The authors distill their advice down to six suggestions in a “[g]uide to avoid being misled by biased presentation and interpretation of data, the first [suggestion] of which is to:  “Read only the Methods and Results sections; bypass the Discuss section.”  Id. at 1093 (emphasis added).

The federal courts have generally been oblivious to the problem of permitting fulsome presentation of hearsay opinions from the discussion and conclusion sections of articles relied upon by testifying expert witnesses.

The Supreme Court’s decision in Joiner provides a striking example.  The Court correctly assessed that plaintiffs’ expert witnesses in that case were relying upon pathologically deficient and unreliable evidence.  (Some of the expert witnesses in Joiner are known repeated offenders against Rule 702.)  In reaching the right result, and in advancing the jurisprudence of the reliability of expert witness opinion testimony, Joiner, however, stumbled in its analysis of the role of reliance upon published studies.  In his opinion in Joiner, Chief Justice Rehnquist gave considerable weight to the consideration that the plaintiffs’ expert witnesses relied upon studies, the authors of which explicitly refused to interpret as supporting a conclusion of human disease causation.  See General Electric Co. v. Joiner, 522 U.S. 136, 145-46 (1997) (noting that the PCB studies at issue did not support expert witnesses’ conclusion that PCB exposure caused cancer because the study authors, who conducted the research, were not willing to endorse a conclusion of causation).

Although the PCB study authors were well justified in their respective papers in refraining from over-interpreting their data and analyses, this consideration is of doubtful general value in evaluating the reliability of an expert witness’s proposed testimony.  First, as some plaintiffs’ counsel have argued, the testifying expert witness may be relying upon a more extensive and supportive evidentiary display than considered by the study authors.  The study, standing alone, might not support causation, but when considered with other evidence, the study could take on some importance in supporting a causal conclusion.  (This consideration would surely not save the sadly deficient opinions challenged in Joiner.) Second, as I have pointed out above, the Discussion sections of published papers of little value.  They are almost never comprehensive reviews of the subject matter, and they are often little more than the personal opinions of the study authors.  Peer reviewers may call for some acknowledgments of the weaknesses of the study, but the authors are generally allowed to press their speculations unchecked.

The use of a paper’s Discussion section to measure the reliability of a proffered expert testimony runs contrary to how scientists generally read and interpret papers.  Chief Justice Rehnquist’s emphasis upon the study authors’ Discussion of their own studies ignores the first important principal of interpreting medical studies, in an evidence-based world view:  In critically reading and evaluating a study, one should ignore anything in the paper other than the Methods and Results sections.

Joiner’s misplaced emphasis upon study authors’ Discussion sections has gained a foothold in the case law interpreting Rule 702.  In Huss v. Gayden, 571 F.3d 442  (5th Cir. 2009), for example, the Court declared:

“It is axiomatic that causation testimony is inadmissible if an expert relies upon studies or publications, the authors of which were themselves unwilling to conclude that causation had been proven.”

Id. (citing Vargas v. Lee, 317 F.3d 498, 501-01 (5th Cir. 2003) (noting that studies that did not themselves embrace causal conclusions undermined the reliability of the plaintiffs’ expert witness’s testimony that trauma caused fibromyalgia), and McClain v. Metabolife Int’l, Inc., 401 F.3d 1233, 1247-48 (11th Cir. 2005) (expert witnesses’ reliance upon studies that did not reach causal conclusions about ephedrine supported the challenge to the reliability of their proffered opinions).

The reference to what authors of relied upon papers state, in Joiner, perpetuates an authority-based view of science to the detriment of requiring good and sufficient reasons to support the testifying expert witnesses’ opinions.  The problem with Joiner’s suggestion that expert witness opinion should not be admissible if it disagrees with the study authors’ Discussion section is that sometimes study authors grossly over-interpret their data.  When it comes to scientific studies written by “political scientists” (scientists who see their work as advancing a political cause or agenda), then the Discussion section often becomes a fertile source of unreliable, speculative opinions that should not be given credence in Rule 104(a) contexts, and certainly should not be admissible in trials.

Perhaps the Discussion section, in the context of a Rule 104(a) proceeding, has some role in evaluating the challenged expert witness’s opinion, but surely it is a weak factor at best.  And clearly, the disagreement with the study authors’ conclusions or opinions, as reflected by speculative Discussion sections, can cut both ways.  Study authors may downplay their findings – appropriately or inappropriately, but study authors often overplay their findings and distort or misinterpret how their findings fit into the full picture of other studies and other evidence.  The quality of peer-reviewed publications is simply too irregular and unpredictable to make the subjective, evaluative comments in hearsay papers the touchstone for admissibility or inadmissibility.

There have been, and will continue to be, occasions in which published studies contain data, relevant and important to the causation issue, but which studies also contain speculative, personal opinions expressed in the Introduction and Discussion sections.  The parties’ expert witnesses may disagree with those opinions, but such disagreements hardly reflect poorly upon the testifying witnesses.  Neither sides’ expert witnesses should be judged by those out-of-court opinions.  Perhaps the hearsay Discussion section may be considered under Rule 104(a), which suspends the application of the Rules of Evidence, but it should hardly be an important or dispositive factor, other than raising questions for the reviewing court.

Expert witnesses should not be constrained or excluded for relying upon study data, when they disagree with the hearsay authors’ conclusions or discussions.  Given how many journals cater to advocacy scientists, and how variable the quality of peer review is, testifying expert witnesses should be required to have the expertise to interpret the data without substantial reliance upon, or reference to, the interpretative comments in the published literature.

VIII.  The Relationship Between Rules 703 and 705

Rule 705 simply provides:

The expert may testify in terms of opinion or inference and give reasons therefor 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.

Rule 705, despite its brevity and apparent simplicity, encourages radical changes in the presentation of expert witness testimony in the courtroom.  Rule 705 permits expert witnesses to give opinions in the most conclusory terms.  Combined with Rule 703’s removal of admissibility as a requirement for materials “reasonably relied upon” by the expert witness, Rule 705 achieves the collapsing of difficult, technical issues into sound bites for juries and judges who increasingly suffer from inability to give sustained attention to such matters.  Under the banner of “convenience” and “economy,” these Rules operate to shift the burden to the crossexaminer to elicit the bases of an expert’s opinion as well as to then engage the expert witness on the reasonableness of his reliance, his methodology, and his application of method to the facts of the case, admissible or not.

The upshot of these changes is that the direct examination of an expert witness can often be very short, and it can be filled up with details of the expert witness’s qualifications and thinly veiled attempts to accredit the witness, even in advance of any attack on credibility.  The expert can then state his opinion as a conclusion, without any of the “messy” research facts or data, or other details.  The crossexaminer is left to dig through the bases, with judge and jury looking impatiently at the clock.  This imbalance creates practical and equitable hardships in how the Federal Rules allocate responsibility for developing factual bases for expert witness opinion between presenting and opposing counsel.  When courts impose time limits in trial of complex matters, the inequity created by the modern Rule 703 is compounded.[xv] Rule 705 gives trial courts discretion to require disclosure of bases.  In the proper case, counsel must be vigilant to motions to require this disclosure before the expert witness delivers his opinion.


Although Rule 703 successfully addresses some evidentiary problems in presenting expert witness opinion testimony, serious problems remain.  The Rule continues to permit expert witnesses to serve as conduits for inadmissible evidence, including opinion evidence that may escape the gatekeeping of Rule 702.  As legal scholars have pointed out, the Rule raises basic issues of fundamental fairness and constitutionality in both civil and criminal proceedings.[xvi] It is time for the Advisory Committee to go beyond restyling the Rule, and to reconsider its substance.

{This post is a revision of my article in article in 7 Proof 3 (Spring 2009).   An earlier version of that article was presented as part of an ALI-ABA Course of Study, “Opinion and Expert Testimony in Federal and State Courts,” on February 15, 2008, in San Diego, California.}

[i] Although elsewhere in the Federal Rules, the Advisory Committee disparaged limiting instructions, commentators and some courts engaged in the “judicial deception” of instructing the jury to accept the inadmissible basis as part of the explanation for the expert witness’s opinion, but not to accept or consider the basis for its truth.  See United States v. Grunewald, 233 F.2d 556, 574 (2d Cir. 1956)(“judicial deception”)(Frank, J.); Nash v. United States, 54 F.2d 1006, 1007 (2d Cir. 1932)(“mental gymnastic”)( Hand, J.).  Not only would such limiting instructions aggravate the problem by giving emphasis to the inadmissible evidence, the instructions surely would confuse most reasonable people who are trying to understand whether an expert witness has applied a reliable method to correctly ascertained “facts or data.”  The bases of an expert witness’s opinion are irrelevant if they do not have some evidential support.

[ii] Peteet v. Dow Chemical Co., 868 F.2d 1428, 1432 (8th Cir. 1989)(“[T]he trial court should defer to the expert’s opinion of what they find reasonably reliable.”); United States v. Sims, 514 F.2d 147 (9th Cir. 1975)(Rule 703 enacted, but not yet in effect)(affirming trial court’s allowing government’s psychologist to rely upon I.R.S. agent’s statement that defendant had previous “legal difficulties” to counter defendant’s claim of recent insanity against tax enforcement).

[iii] International Adhesive Coating Co. v. Bolton Emerson International, Inc., 851 F.2d 540, 544-45 (1st Cir. 1988)(equating reasonableness with “normal practice”).

[iv] United States v. Locascio, 6 F.3d 924, 938 (2d Cir. 1993).  The Third Circuit, which had adopted an extremely laissez-faire approach to expert witness testimony, signaled its compliance with the Supreme Court’s decision in Daubert, in In re Paoli Railroad Yard PCB Litigation:

We now make clear that it is the judge who makes the determination of reasonable reliance, and that for the judge to make the factual determination under Rule 104(a) that an expert is basing his or her opinion on a type of data reasonably relied upon by experts, the judge must conduct an independent evaluation into reasonableness.  The judge can of course take into account the particular expert’s opinion that experts reasonably rely on that type of data, as well as the opinions of other experts as to its reliability, but the judge can also take into account other factors he or she deems relevant.

35 F.3d 717, 748 (3d Cir. 1994)(emphasis in original).

[v] In re Agent Orange Product Liability Lit., 611 F. Supp. 1223 (E.D.N.Y. 1985), aff’d on other grounds, 818 F.2d 187 (2d Cir. 1987), cert. denied, 487 U.S. 1234 (1988).

[vi] 611 F. Supp. at 1246.  But see Fed. R. Evid. 803(4).

[vii] See, e.g., Soldo v. Sandoz Pharm. Corp., 244 F.Supp. 2d 434, 572 (W.D.Pa. 2003)(barring expert witness opinion testimony, under Rule 702 and 703).

[viii] See, e.g., Ealy v. Richardson-Merrell, Inc., 897 F.2d 1159, 1161-62 (D.C. Cir. 1990)(affirming exclusion of an expert whose opinion lacked scientific foundation, and ignored extensive contrary, published data); Lima v. United States, 708 F.2d 502, 508 (10th Cir. 1983)(affirming exclusion of epidemiologist who relied upon data not reasonably relied upon by experts in the fields of epidemiology and neurology).

[ix] See, e.g., Opinion, N.J. Super. Ct., Middlesex Cty., Docket L-5532-01-MT (denying motion to preclude expert witnesses from relying, in part, on unpublished study)(Garruto, J.).  This issue was anticipated in one of the leading cases on expert witness opinion testimony.  In re Paoli, 35 F.3d 717, 749 n. 19 (3d Cir. 1994)(pointing out that Rules 702 and 703 were not redundant, and that reliable opinions might be partially based upon unreliable data).

[x]See Beech Aircraft v. Rainey, 488 U.S. 153, 168 (1988)(“The distinction between statements of facts and opinion is, at best, one of degree.”)

[xi] American Key Corp. v. Cole Nat’l Corp., 762 F.2d 1569, 1580 (11th Cir. 1985)(“Expert opinions ordinarily cannot be based upon the opinions of others whether those opinions are in evidence or not.”); see also TK-7 Corp. v. Estate of Barbouti, 993 F.2d 722, 732 (10th Cir. 1993)(affirming exclusion of expert testimony under Rule 703 “where the expert failed to demonstrate any basis for concluding that another individual’s opinion on a subjective financial prediction was reliable, other than the fact that it was the opinion of someone he believed to be an expert who had a financial interest in making an accurate prediction”).

[xii] See, e.g., Lewis v. Rego Co.,757 F.2d 66, 73-74 (3d Cir. 1985)(holding that trial court had erred in excluding a testifying expert witness’s recounting of, and reliance upon, an out-of-court conversation with a non-testifying expert).  See also Barris v. Bob’s Drag Chutes & Safety Equipment, 685 F. 94, 102 n.10 (3d Cir. 1982)(“Under Rule 703, an expert’s testimony may be formulated by the use of the facts, data and conclusions of other experts.”); Seese v. Volkswagenwerk A.G., 648 F.2d 833, 845 (affirming admissibility, under Rule 703, of accident-reconstruction expert, whose opinion was based upon facts, data, and conclusions of a physician).

[xiii] Advisory Committee Note to Rule 703 (emphasis added).

[xiv] Fed. R. Evid. 803(6).

[xv] Evidentiary rules in state courts, even those states that have adopted Rule 703, vary considerably in how disclosure is required or allowed.  Pennsylvania, for instance, has adopted its Rule 703 verbatim from the Federal Rules, but it handles disclosure very differently under its version of Rule 705:

The expert may testify in terms of opinion or inference and give reasons therefore; however the expert must testify as to the facts or data on which the opinion or inference is based.

Pa. R. Evid. 705 (emphasis added).  See, e.g., Hansen v. Wyeth, Inc., 72 Pa. D. & C. 4th 225, 2005 WL 1114512, at *13, *19 (Phila. Ct. Common Pleas 2005)(Bernstein, J.)(granting new trial to verdict loser as result of expert witness’s failure or inability to provide all bases for his opinion).

[xvi] See, e.g., Seaman, “Triangulating Testimonial Hearsay:  The Constitutional Boundaries of Expert Opinion Testimony,” 96 Georgetown L.J. 827 (2008).

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