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June 21, 2016 Articles

Jenga for Experts: How Much Can One Expert Rely on Another?

By Eric E. Hudson and Richelle W. Kidder

Particularly in mass tort litigation, attorneys often face choices about how many experts to disclose, what specialty (or specialties) are necessary for the litigation, and—as part and parcel of those considerations—whether one expert witness can address topics that ideally might be handled by another expert or even by other non-designated witnesses. Minimizing the total number of expert witnesses may be strategically appropriate for a variety of reasons: It can make a case more palatable for the jury, and it can be an effective way to reduce costs to the client. Courts also may limit the number of experts under case management orders.

Against these competing interests, counsel must balance the need for efficiency with the limitations imposed by civil rules and case law. This article explores, under federal law, instances where experts may offer opinions based on other experts’ opinions, as well as situations where an expert may rely on an undisclosed witness’s findings to support his or her opinion.

Engaging in this balancing act is not without risks, perhaps akin to a game of Jenga: If the court strikes the underlying expert’s (or witness’s) testimony, then other, surviving experts may be left on a precariously thin surface. This article examines those scenarios, contrasts situations where the court found an expert’s reliance on another expert or witness or materials to be permissible and appropriate, and concludes by offering a few suggestions to strengthen an expert’s foundation.

The Basic Building Block
Federal Rule of Evidence 703 provides the foundation for permitting an expert to rely on another witness or underlying materials. Titled “Bases of Opinion Testimony by Experts,” Rule 703 states in full as follows:

An expert may base an opinion on facts or data in the case that the expert has been made aware of or personally observed. If experts in the particular field would reasonably rely on those kinds of facts or data in forming an opinion on the subject, they need not be admissible for the opinion to be admitted. But if the facts or data would otherwise be inadmissible, the proponent of the opinion may disclose them to the jury only if their probative value in helping the jury evaluate the opinion substantially outweighs their prejudicial effect.

Put differently, an expert is entitled to rely even on inadmissible facts or data where the “magic phrase” in Rule 703 has been satisfied: i.e., that the items are the “kinds of facts or data” that “experts in the particular field would reasonably rely on.” There is, accordingly, support in the plain text of the rule to permit one expert to rely on another expert, another witness, or other facts or data.

Case law supports this basic proposition. For instance, a physician expert’s reference to an underlying pathology report may be considered “routine procedure in medical treatment” and thus appropriate and permissible under Rule 703 (as well as Rule 702). See, e.g., Holbrook v. Lykes Bros. S.S. Co., 80 F.3d 777, 781–82 (3d Cir. 1996) (physician’s reliance on a pathology report to confirm his diagnosis did not reflect negatively on his qualifications or ability to diagnose his patient; to the contrary, it reflected routine procedure in medical treatment, as recognized by Rule 703); see also, e.g., Keller v. Feasterville Family Health Care Ctr., 557 F. Supp. 2d 671, 681 (E.D. Pa. 2008) (“[N]o support exists in the text or history of the Federal Rules of Evidence, or case law to limit an expert from reviewing and referring to the opinions of other experts. . . . Thus, even if [Expert A] relied solely on [Expert B’s] testimony, his reliance would be proper because physicians generally rely on a specialist’s interpretation of data.”).

These holdings are closely aligned with language from the 1972 advisory committee notes to Rule 703:

Facts or data upon which expert opinions are based may, under the rule, be derived from three possible sources. The first is the firsthand observation of the witness, with opinions based thereon traditionally allowed. A treating physician affords an example. Rheingold, The Basis of Medical Testimony, 15 Vand.L.Rev. 473, 489 (1962). Whether he must first relate his observations is treated in Rule 705. The second source, presentation at the trial, also reflects existing practice. The technique may be the familiar hypothetical question or having the expert attend the trial and hear the testimony establishing the facts. Problems of determining what testimony the expert relied upon, when the latter technique is employed and the testimony is in conflict, may be resolved by resort to Rule 705. The third source contemplated by the rule consists of presentation of data to the expert outside of court and other than by his own perception. In this respect the rule is designed to broaden the basis for expert opinions beyond that current in many jurisdictions and to bring the judicial practice into line with the practice of the experts themselves when not in court. 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.

Steady, Now
Having begun with the basic premise that experts may appropriately rely on other people or information in forming their conclusions, it is worthwhile to evaluate possible weak points in the strategy of one expert relying on another. As explained below, federal courts have excluded certain experts deemed to be “merely a mouthpiece for,” “merely parroting,” or “merely regurgitating” another expert’s or witness’s findings and conclusions. Led by Judge Posner’s opinion in Dura Automotive Systems of Indiana, Inc. v. CTS Corp., 285 F.3d 609 (7th Cir. 2002), there are traps in the rules (of evidence and civil procedure) for the unwary expert who seeks to rely on another witness’s underlying reports or work in formulating his or her opinion.

Dura was a case involving cleanup of an Environmental Protection Agency Superfund site. Dura designated only one expert, a hydrogeologist, who admitted at his deposition that he was not an expert in mathematical models of groundwater flow. Instead, he relied on mathematical modeling prepared by other employees of his firm. CTS moved to exclude that expert, and Dura responded by submitting affidavits from four employees who worked on the underlying mathematical models.

CTS moved to strike those affidavits as untimely under Rule 37. The district court granted the motion to strike. Without those affidavits, there was insufficient evidence of the reliability of the models that the expert relied on—so the court excluded Dura’s expert. In a one-two punch, because Dura had no expert, summary judgment was granted in CTS’s favor.

The issue on appeal was whether the district court properly struck the underlying affidavits. The Seventh Circuit affirmed, and Judge Posner framed the issue, in part, as follows:

[T]o the extent that the affidavits contain evidence that would have to be presented at trial by an expert witness [other than the designated expert] to withstand a motion for judgment as a matter of law, Dura’s failure to have made timely disclosure of their expert opinions invited application of Rule 37(c)(1) to bar the authors of the affidavits, or any other expert for that matter, from testifying along with [the designated expert]. 

Dura, 285 F.3d at 612.

Judge Posner began from a threshold premise: There is nothing wrong with an expert using “assistants” (as in this case, the employees at the expert’s firm) to formulate an expert opinion, because the opposing party may depose them and the expert to determine if Rule 703 has been satisfied. The court continued, however, that “[a]nalysis becomes more complicated if the assistants aren’t merely gofers or data gatherers but exercise professional judgment that is beyond the expert’s ken.” The court cited Rule 703’s advisory committee notes, which provide the example of a “physician who, though not an expert in radiology, relies for a diagnosis on an x-ray. We too do not ‘believe that the leader of a clinical medical team must be qualified as an expert in every individual discipline encompassed by the team in order to testify as to the team’s conclusions.’”

The court paused there, though, to consider cases in which the “soundness of the underlying expert judgment is in issue.” In that situation, the expert who evaluates the issue is “the one who should have testified.” As Judge Posner wrote, in a now-oft-quoted passage,

[t]he Daubert test must be applied with due regard for the specialization of modern science. A scientist, however well credentialed he may be, is not permitted to be the mouthpiece of a scientist in a different specialty. That would not be responsible science. A theoretical economist, however able, would not be allowed to testify to the findings of an econometric study conducted by another economist if he lacked expertise in econometrics and the study raised questions that only an econometrician could answer. If it were apparent that the study was not cut and dried, the author would have to testify; he could not hide behind the theoretician.

Id. at 614.

Applied to the Dura case, the court of appeals found that the district court properly struck the underlying affidavits regarding mathematical modeling because they reflected an “iterative process” that required discretionary judgments by the affiants:

It is apparent from these affidavits that the [designated expert’s] assistants did not merely collect data for him to massage or apply concededly appropriate techniques in a concededly appropriate manner, or otherwise perform routine procedures, and that he himself lacks the necessary expertise to determine whether the techniques were appropriately chosen and applied.

Id. at 615.

Thus, “[w]ithout [the assistants’] testimony . . . [the designated expert’s] testimony would have rested on air.” The court of appeals thus affirmed the district court’s striking of the affidavits—and accordingly affirmed the application of Rule 37(c)(1), which provides that expert testimony may not be presented if the expert’s report was not disclosed under Rule 26.

Federal courts, at the appellate level, have followed Dura or applied similar rationale. See, e.g., Mike’s Train House, Inc. v. Lionel, L.L.C., 472 F.3d 398, 403 (6th Cir. 2006); Turner v. Burlington N. Santa Fe R.R. Co., 338 F.3d 1058, 1060–62 (9th Cir. 2003). See also Sigler v. Am. Honda Motor Co., 532 F.3d 469, 479 (6th Cir. 2008) (affirming exclusion of the plaintiff’s expert mechanic who had relied on materials prepared by an accident reconstructionist; although not explicit, the court appears to have excluded under Rule 702 (qualifications), Rule 702 (reliability), as well as Rule 703 (bases for expert’s opinion)). Some cases pre-date Dura. See, e.g., United States v. Marine Shale Processors, 81 F.3d 1361, 1370 (5th Cir. 1996); United States v. Grey Bear, 883 F.2d 1382, 1392–93 (8th Cir. 1989)

District courts have likewise looked to Dura to exclude an expert’s testimony under Rules 702 and 703. A sampling of representative cases is briefly summarized here: Leese v. Lockheed Martin Corp., 6 F. Supp. 3d 546 (D.N.J. 2014) (expert’s opinion deemed unreliable where he had relied on letter prepared by another witness deemed to not be qualified); United States v. Zolot, 968 F. Supp. 2d 411, 426–27 (D. Mass. 2013) (excluding physician who relied on medical examiner’s diagnosis where he merely repeated the medical examiner’s opinion as the only basis for his own opinion and did not have expertise to independently reach that conclusion); Villagomes v. Lab. Corp. of Am., No. 2:08-CV-00387-RLH, 2010 WL 4628085, at *4 (D. Nev. Nov. 8, 2010) (excluding expert psychiatrist who, in part, relied on other experts’ opinions outside his field); Eberli v. Cirrus Design Corp., 615 F. Supp. 2d 1357 (S.D. Fla. 2009) (excluding expert who made no findings of his own and merely adopted another expert’s metallurgical conclusions); Deutz Corp. v. City Light & Power, Inc., 2009 WL 2986415 (N.D. Ga. Mar. 21, 2009) (excluding expert engineer as not qualified and because he used unreliable methodology where expert simply took conclusions from other reports, particularly where he used the report not only as data but also as substantive evidence for his ultimate conclusions); Bouygues Telecom, S.A. v. Tekelec, 472 F. Supp. 2d 722 (E.D.N.C. 2007) (excluding portions of telecommunications expert’s testimony where the other experts, whose reports he relied on, were initially designated as experts but were withdrawn, and rejecting “the wholesale adoption of the opinion of another expert verbatim”).

Navigating Around the Obstacles

In contrast to the above exclusions, the Court of Claims declined to strike expert testimony in Banks v. United States, 75 Fed. Cl. 294 (Ct. Cl. 2007), a dispute regarding the flow of sand to shoreline property. There, the court permitted an expert who was nota geologist to incorporate geology findings and reports into his Rule 26 report, finding his reliance appropriate under Rule 703: There was overlap between the expert’s field and the geological findings on which he relied, and the geological findings provided a “first level of knowledge” that would “assist him in his own research and findings.” Banks, 75 Fed. Cl. at 304. 

Another example is In re Wright Medical Technology Inc., Conserve Hip Implant Products Liability Litigation, No. 1:13-CV-297-WSD, 2015 WL 5117896 (N.D. Ga. Aug. 31, 2015), in which the plaintiff’s expert relied on the “observations and opinions” of the treating physician, a surgeon. There, the district court found the expert’s testimony admissible under Rule 703:

In view of [the treater’s] considerable background and experience in hip replacement and revision surgeries, the number of instances where he has performed revision surgeries in which metallosis was present, his experience in recognizing and diagnosing it, and his credentials and qualifications as an expert in original and revision hip replacement surgeries, the [court finds his] observations and opinions reliable. Those of Plaintiff’s metallosis experts who rely on [the treater’s] observations, conclusions, and opinions, are entitled to do so. [His] observations, conclusions, and opinions are the kind of medically reliable evidence that medical experts would consider in reaching a conclusion about medical conditions or complications. That is, medical professionals and researchers often rely on the observations of treating physicians to reach diagnostic conclusions, decide on courses of treatment and opine on the commonality of disease and injury among patients to determine if there is a common course of disease or injury. The observations of an experienced treating physician are especially reliable because they serve to record a patient’s medical history and often form the basis for a person’s treatment and health issues throughout the person’s life. In short, it is reasonable for an expert to rely on a treating physician’s observations, comparisons, conclusions, and opinions in seeking to reach a conclusion on the course of a disease, injury, health complication or, in this case, the cause of an undisputed hip replacement device failure. The certainty and sufficiency of the treating physician’s observations and conclusions, of course, may very well impact the persuasiveness of the opinions reached by the expert relying on them.

Id. at *9.

The district court in In re Yasmin & YAZ (Drospirenone) Marketing, Sales Practices & Products Liability Litigation, No. 3:09-MD-02100, 2011 WL 6302889 (S.D. Ill. Dec. 16, 2011), likewise denied a motion to exclude an expert who, in part, relied on other experts. The court found that the expert conducted a “fully independent analysis of the matter.” Id. at *17. Similar conclusions have been reached where the record demonstrated the designated expert was not a “mere mouthpiece,” as proscribed by Dura. See U.S. Gypsum Co. v. Lafarge N. Am. Inc., 670 F. Supp. 2d 748, 759 (N.D. Ill. 2009) (denying motion to exclude expert who relied on other experts, where expert conducted independent analysis to arrive at his conclusions).

A Few Tips to Avoid Collapse
Designating an expert who will, in turn, rely on another expert (or another witness or other materials) warrants an evaluation of risks and benefits—and Dura is a key example of the strategic decisions involved. Ultimately, counsel’s choice for the number of experts in any litigation will likely be driven by court order—or other more fluid considerations, such as overall trial strategy or cost consciousness.

If, based on preference or necessity (or both), an expert must rely on another witness, the case law above sheds some light on minimizing risks. To avoid an expert being called a “mere mouthpiece” (or “parrot” or one who regurgitates findings of another), counsel should, ideally, vet the expert to determine whether his or her opinions are consistent with the underlying witness’s credentials, whether the underlying report or materials can be independently verified or tested, whether the expert has conducted an independent analysis of the available literature, whether the expert has independently reviewed the opinions of the underlying experts, and whether he or she can conclude that reported data are consistent with his or her opinions. Consideration of these matters, plus (ideally) their inclusion in a Rule 26(a)(2) report and preparation for testimony, may prove beneficial in protecting an expert from exclusion.

Keywords: mass torts litigation, expert witness, reliance, exclusion, Federal Rule of Evidence 703

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