INTRODUCTION
Last June's United States Supreme Court decision in Daubert v. Merrell Dow Pharmaceuticals, Inc., (1) rejected the Frye "general acceptance" test for scientific evidence, (2) and went on to make "some general observations"(3) about proper admissibility analysis under Federal Rule of Evidence 702.(4) Daubert was the Court's first decision squarely addressing the expert testimony provisions of the Federal Rules of Evidence, and United States Law Week called Daubert "probably the most important procedural case of the term." (5)
Not surprisingly, Daubert has generated many articles that examine the decision and make broad predictions about the future of expert scientific testimony. Much of this commentary, however, is of limited utility, dwelling excessively on relatively tangential points discussed in Daubert, (6) many of which, as Chief Justice Rehnquist pointed out, "tend to be not only general, but vague and abstract."(7)
The result is often a diffuse analysis that approaches or exceeds in length the decision being "summarized." Daubert is, after all, remarkably short, with the main opinion running about 5000 words and spanning only eight pages in the Supreme Court Reporter.
Worse, many of these commentaries fail to make any serious reference to what the Court repeatedly emphasized is the "focus" of Rule 702: the distinction between the "principles and methodology" sued by an expert and the "conclusions" thereby reached by the expert. (8) This short Essay argues that Daubert is most coherently understood by concentrating on this methodology/conclusion distinction.
I. DAUBERT'S FOCUS ON THE DISTINCTION BETWEEN AN EXPERT'S "METHODOLOGY" AND AN EXPERT'S "CONCLUSION
The focus of Daubert is emphasized by the Court near the end of its opinion, after it has clarified that Rule 702 requires trial judges, in the exercise of their "gatekeeping responsibility," (9) to ensure that a qualified scientific expert is actually testifying to "scientific knowledge." (10) In winding up its analysis, the Court explicitly addressed the narrow focus of Rule 702's scrutiny:
The inquiry envisioned by Rule 702 is, we emphasize, a flexible one. Its overarching subject is the scientific validity-- and thus the evidentiary relevance and reliability-- of the principles that underlie a proposed submission. The focus, of course, must be solely on principles and methodology, not on the conclusions that they generate. (11)
The Court's instructions are quite clear: Rule 702 authorizes courts to scrutinize only the "scientific validity" of the "principles and methodology" used by an expert-- not the persuasiveness of the "conclusions" so generated. An expert's principles and methodology, alone, are the focus of Rule 702.
Daubert's tight focus on the validity of the principles and methodology used by an expert is hardly an aside. The theme is struck in three other parts of the opinion:
1. In the introductory portion of its Rule 702 analysis, the Court states that Rule 702 "clearly contemplates some degree of regulation of the subjects and theories about which an expert may testify" (12)--namely, that "the subject of an expert's testimony must be 'scientific... knowledge.'"(13) Addressing this term, the Court makes clear that science is really defined through its process, not its product. The Court observes that "the adjective 'scientific' implies a grounding in the methods and procedures of science."(14) And the Court endorses the analysis of leading scientific organizations that science consists not of "'an encyclopedic body of knowledge about the universe, '"but rather"' represents a process for proposing and refining theoretical explanations about the world that are subject to further testing and refinement.'" (15) In other words, if a scientific expert uses scientifically valid principles and methodologies in analyzing an issue, her testimony is, by definition, "scientific knowledge" within the meaning or Rule 702, and is therefore admissible.
(2) In a footnote to its key "focus" paragraph, the Court surveys the approach to scientific evidence taken by a number of prominent commentators. The Court endorses their approaches in broad outline, but only "to the extent that they focus on the reliability of evidence as ensured by the scientific validity of it underlying principles." (16) Similarly, in an earlier definitional footnote also citing commentary, the Court indicates that" in a case involving scientific evidence, evidentiary reliability will be based upon scientific validity." (17)
(3) Finally, the Court returns to its core focus in the last substantive paragraph of its opinion, where it summarizes its Rule 702 analysis: "Pertinent evidence based on scientifically valid principles will satisfy" (18) the demands of the Federal Rules of Evidence.
These repeated references to principles and methodology demonstrate that the Court in Daubert knew what it meant, and meant what it said, about the "focus" of Rule 702. Moreover, the Court's analysis was hardly novel. The Court was following a line of analysis that has enjoyed broad support in the lower federal courts for the past decade, beginning with the District of Columbia Circuit's decision in Ferebee v. Chevron Chemical Co. (19) Ferebee reviewed an apparently unprecedented expert factual conclusion-- which no published literature supported-- that a worker's long-term exposure to the herbicide paraquat caused his death. (20) Extant literature had demonstrated only short-term effects of paraquat at much higher doses. The D.C. Circuit held that if expert testimony, "while controversial in its conclusion, is based on well-founded methodologies," it is admissible. (21) After all, the court noted: "The experts on both sides relied on essentially the same diagnostic methodology; they differed solely on the conclusions they drew from test results and other information. The case was thus a classic battle of the experts, a battle in which the jury must decide the victor." (22) Any contrary approach, which would give judges license to weigh the credibility of the conclusions that qualified experts reach using concededly valid methodologies, has no support in evidence law and would usurp the function of the trier of fact. (23) Post-Ferebee cases thus have routinely insisted on the distinction -- ultimately adopted in Daubert-- between scrutiny of an expert's methodology an scrutiny of an expert's conclusion.(24)
II. TAKING THE METHODOLOGY/CONCLUSION
DISTINCTION SERIOUSLY
Given the clear distinction drawn in Daubert between an expert's methodology and conclusion, what must be done to ensure that the Court's distinction is taken seriously? Two important implications of Daubert for judicial decision making should be notes.
First, and by far most significant, it is completely inappropriate for either the proponent of scientific testimony or her opponent to advance Rule 702 admissibility arguments that depend on the ultimate conclusion reached by an expert. A party who refers in the Rule 702 context to an expert's ultimate conclusion, whether to support or to attack admissibility, will merely cast doubt on her own arguments concerning methodology by signaling that those arguments are too weak to prevail without resort to characterizations about the strength of the expert's ultimate conclusion. The issue under Rule 702, "of course," is "solely" whether the methodology and principles that an expert uses in providing testimony are valid-- not where the expert ultimately comes out. (25) This rule applies regardless of how favorably the expert's conclusion is viewed: that a judge finds an expert's conclusion persuasive does not meant that the expert has used a valid methodology to reach that conclusion; conversely, that a judge regards an expert's conclusion as unpersuasive does not meant that an invalid methodology has been employed.
The effect of this rule is well illustrated by the Daubert case itself, in which the defendant's frequent emphasis on expert conclusions proved futile.
The underlying facts of Daubert involved claims that the anti-nausea drug Bendectin had caused birth defects in two children. (26) The defendant, Merrell Dow Pharmaceuticals, Inc. ("Merrell"), "moved for summary judgment, contending that Bendectin does not cause birth defects in humans and that [plaintiffs] would be unable to come forward with any admissible evidence tht it does."(27) In support, Merrell produced an affidavit of an epidemiologist who concluded on the basis of published epidemiological studies tht Bendectin is not "a risk factor for human birth defects." (28)
On the issue of methodology, the record was clear: several of plaintiffs' experts, and several of Merrell's experts who had testified in other cases, all agreed tht the valid methodology for forming an ultimate judgment on whether Bendectin is a risk factor for human birth defects requires review of four key sources of information (in vitro laboratory studies, in vivo animal studies, pharmacological studies on chemical structure, and human epidemiological studies) and consideration of the collective meaning of these data. (29) Further, the testimony of the plaintiffs' experts that they in fact used this concededly valid methodology in rendering their opinions was uncontradicted on the record. (30)
Merrell's strategy in the Supreme Court was to ignore the
uncontradicted recorded establishing that plaintiffs' experts were using a valid methodology and instead to argue: 1. that there was an overwhelming consensus among experts who had studied Bendectin that the drug was perfectly safe and could never cause birth defects, and 2. that because plaintiffs' experts had reached a contrary conclusion, their testimony must be inadmissible. Merrell's position was that the persuasiveness of an expert's conclusion is germane to admissibility under Rule 702. Thus, in opposing Supreme Court review, Merrell argued tht the courts below had properly rejected plaintiffs' "pleas to be permitted to swim upstream against an overwhelming scientific torrent of consensus tht Bendectin does not cause limb reduction birth defects." (31) Merrell claimed that plaintiffs were guilty of "heresy" in attempting to proffer expert testimony to contradict a "universally recognized scientific truth []," one "as elementary, and as widely accepted as the laws of gravity." (32) After the Court granted review, Merrell persisted in making detailed factual arguments that plaintiffs' experts had drawn the wrong conclusion from the data about Bendectin. (33)
But nowhere did Merrell articulate any legal rationale for why the conclusion reached by an expert bears on the Rule 702 admissibility inquiry, as long as the expert is using a proper methodology. Rather, Merrell simply asserted that there was no way to draw a distinction between methodology and conclusion based on Rule 702 does not apply to 'the substance of the opinions; but only to 'the techniques that are being analyzed.'"(34) Merrell insisted, however, tht "it is hard to see how to derive [plaintiffs;] distinction from Rule 702."(35) Further, Merrell attempted to muddy the methodology/conclusion distinction through what might be termed a "litigation-by-thesaurus" strategy. Merrell simply invented ambiguous phrases that lumped together the concepts of methodology and conclusion, in an effort to obscure the distinction between the two.(36)
Merrell's effort was unsuccessful. The Court refused to lump together these two disparate aspects of an expert's testimony, and instead insisted that the "focus" of Rule 702 must "of course" be "solely" on the methodology and principles used by the expert, not on the conclusions. (37) In a further rebuke, the Court completely ignored Merrell's extensive factual arguments relating to the conclusion of plaintiffs' experts. In fact, far from endorsing Merrell's attacks on plaintiffs' experts, the Court lauded their "impressive credentials." (38) Merrell's extended description of other scientists' supposedly overwhelming contrary conclusions was treated as irrelevant under Rule 702. The Court's response to Merrell's strategy concretely demonstrates that even the most fervent disagreements with an expert's conclusion are irrelevant under Rule 702.
That Rule 702 concerns only the general methodology employed by an expert, and does not authorize scrutiny of the ultimate conclusion reached by that expert after applying that methodology to a given set of facts, is made doubly clear by reference to the provision of the Federal Rules of Evidence governing judicial notice. Rule 201(b) permits judicial notice of any adjudicative fact that is "not subject to reasonable dispute" because it is "capable of accurate and ready determination by resort to sources whose accuracy cannot reasonably be questioned."(39) Rule 201(b) thus is the evidence rule that suggests a limit for what conclusion an expert may reach using a valid methodology. If given fact cannot "reasonably be questioned" because it can be accurately and readily
determined from authoritative sources, then an expert presumably should not be permitted to testify to the opposite conclusion. As the Fifth Circuit noted in one case refusing to permit the exclusion of an expert's conclusion on the theory that it was "controversial," "this approach [cannot] be carried to extremes-- to, for example, the denial of gravity or the like."(40) Conversely, however, when a fact is "subject to reasonable dispute"(41) because the stringent requirements for judicial notice are not satisfied, then an expert is permitted to reach a "controversial" conclusion on the issue. This will be the case "where science has some meaningful information but scientific 'truth' has not so completely hardened as to prevent legitimate difference of true expert opinion in a particular concrete context."(42)
A second implication of Daubert for judicial decision making involves Daubert's probable effect in streamlining summary judgment analysis in many cases. The Supreme Court has made clear that, in analyzing the validity of th methodology and principles used by an expert to address a given question, a trial judge must rule on the issue based on the record, in an exercise of her fact-finding duties under Federal Rule of Evidence 104(a). (43) Therefore, before offering any case-specific analysis of acts, or indicating an ultimate conclusion, each expert whose testimony is proffered by a party must explain at the outset the methodology that she intends to use, and why it is a valid methodology. Further, the Court has insisted, the expert must demonstrate that her methodology meets what Judge Edward R. Becker of the Third Circuit has termed the requirement of "fit." (44) It is not enough for a methodology to be valid in the abstract, for some purposes; it must have "a valid scientific connection to the pertinent inquiry as a precondition to admissibility." (45) For example, a physician's use of a stethoscope is certainly a valid methodology for determining a patient's pulse, but presumably is not a valid methodology, taken alone, for determining the cause of a patient's cancer.
That all experts must explain and validate their general methodology at the outset should significantly streamline summary judgment procedures in those substantive areas where widespread agreement exists on the appropriate methodologies of addressing particular issues. In the toxic tort field, for example, the methodology of "differential diagnosis" typically is the means by which a physician assesses the possible or probable causes of a medical condition. When n one part (usually the defendant) moves for summary judgment, usually that party will attach expert affidavits negating a particular fact, pursuant to Federal Rules of Civil Procedure 56(c). If the movant's experts are using a standard methodology and validate that methodology, and if the opposing experts use the same methodology (as was the case in Ferebee), then any Rule 702 dispute over methodology will drop out, avoiding the need for laborious analysis by the trial judge. Standard scientific methodologies abound in many other fields of litigation.
Careful attention to the methodology used by the movant's experts thus may significantly streamline a trial summary judgment duties under Rule 702.
CONCLUSION
Despite the ever-expanding volume of commentary on Daubert, closes attention to the Court's explanation of the "focus" of Rule 702 reveals a clear and rigorous, but streamlined, framework for analysis of expert scientific testimony. As long as this "focus" remains at the center of attention of both attorneys and judges, the Court's effort in Daubert to clarify the "nature and source" of the "gatekeeping" duty under Rule 702 (46) will not have been in vain.
* J.D., Harvard Law School, 1986. Mr. Chesbro practices in Cambridge, Massachusetts, specializing in appellate and constitutional litigation. He has litigated a wide range of United States Supreme Court cases, most recently serving as counsel of record for the winning parties in Daubert v. Merrell Dow Pharmaceuticals, INC., 113 S. CT. 2786 (1993), and TXO Prod. Corp. v. Alliance Resources Corp., 113 S. Ct. 2711 (1993).
(1) 113 S. Ct. 2786 (1993).
(2) Id. at 2792-94; see Frye v. United States, 293 F. 1013 (D.C. Cir. 1923)
(3) Daubert, 113 S. Ct. at 2796.
(4) Id. at 2796-98 (citing FED. R. EVID. 702).
(5) Review of Supreme Court's Term, 62 U.S.L.W.3101, 3108 (US. Aug. 17, 1993).
(6) See, e.g., David E. Bernstein & Peter W. Huber, Defense Perspective, 1 SHEPARD'S EXPERT & SCI. EVIDENCE Q. 59 (1993); Michael Hoenig, The New Reliability Test for Expert Testimony, N.Y.L.J., July 12, 1993, at 3; Thomas W. Kirby, Putting Expert Under Scrutiny, LEGAL TIMES, July 26, 1993, at 538; Michael Martin, Admissibility After 'Daubert,' N.Y.L.J., Aug. 13, 1993, at 3.
(7) Daubert, 113 S. Ct. at 2799 (Rehnquist, C.J., joined by Stevens, J., concurring part and dissenting in part)>
(8) Id. at 2797
(9) Id. at 2795 n.7.
(10) Id. at 2794-97.
(11) Id. at 2797 (footnote omitted).
(12) Id. at 2795.
(13) Id. (quoting FED. R. EVID. 702).
(14) Id. (emphasis added).
(15) Id. (citation omitted).
(16) Id. at 2797 n. 12.
(17) Id. at 2795 n. 9.
(18) Id. at 2799 (emphasis added)
(19) 736 F.2d 1529 (D.C. Cir.), cert. denied, 469 U.S. 1062 (1984)
(20) Id. at 1533.
(21) Id. at 1535.
(22) Id.
(23) See 11 JAMES W. MOORE & HELEN I. BENDIX, MOORE'S FEDERAL PRACTICE ss 77702.30[2] (2d ed. 1993).
(24)See, e.g., Celia v. United States, 998 F.2d 418, 426 (6th Cir. 1993) ("Although [the expert's] conclusion differs from those of the defendant's medical experts, he has utilized an accepted methodology in reaching his conclusion -- namely, analysis of medical literature and case study comparison with the individual characteristics of the patient's case to determine etiology."); Christophersen v. Allied-Signal Corp., 939 F.2d 1106, 111 & n.9 (5th Cir. 1991) (en banc) (stating that the proper analysis is not whether an expert's conclusion is correct, but "whether in reaching his conclusion, the witness used a well-founded methodology or mode of reasoning," and reaffirming circuit precedent that "[a]s long as the expert's methodology is well founded, the nature of the expert's conclusion is generally irrelevant, even if it controversial or unique"; that "'an expert's opinion need not be generally accepted in the scientific community before it can be sufficiently reliable and probative in support of a jury finding'"; and that federal courts are not in the business of attempting "to determine which expert's conclusion [is] more in line with the consensus in the scientific community") (citation omitted) (emphasis added), cert. denied, 112 S. Ct. 1280 (1992); Hines v. Consolidated Rail Corp., 926 F. 2d 262, 274 (3d Cir. 1991) (though [the expert's] opinion could be considered to be 'novel,' it appears that under the [Rule 702] standard, his methods were not"); Osburn v. Anchor Lab., Inc., 825 F. 2d 908, 915 (5th Cir. 1987) ("an expert's opinion need not be generally accepted finding," and medical expert opinion testimony that is controversial in its conclusions can support a jury finding of causation as long as the doctor's conclusory opinion is based upon well-founded methodologies") (citations omitted), cert. denied, 485 U.S. 1009 (1988).
(25) Daubert, 113 S. Ct. at 2797
(26) Id. at 2791-92.
(27) Id. at 2791.
(28) Id.
(29) Brief for Petitioners at 4-6, Daubert (No 92-102).
(30) Id. at 6-11.
(31) Respondent's Brief in Opposition at 1, Daubert (No. 92-102).
(32) Id. at 1-2, 3-4.
(33) E.g., Brief for Respondent at 5, Daubert (No. 92-102) (arguing that the conclusion of plaintiff's experts contradicts a "massive body of uniform scientific research"); Id. at 11 (asserting the existence of a "near-library," an "overwhelming body of data that contradict their conclusion")
(34) Id. at 16 n.9 (quoting Plaintiffs' Reply Brief at 10, Daubert's 951 F.2d 1128 (9th Cir. 1991) (No. 90-55397))
(35) Id. at 17 n. 9.
(36) See, e.g., Brief for Respondent, supra note 33, at 9 (suggesting "adequate foundation" requirement)(; Id. at 10 ("reliable foundation" test); Id. at 12 ("conclusions that are validated" test); Id. at 17 ("natural 'accepted-standards-for-validation' meaning" for Rule
702); Id. at 21 ("'foundation' requirement"); Id. at 22 (judge should "screen evidence based on its substance"); Id. ("foundational inquiry" test); Id. at 24 ("foundation filter"); Id. at 26 ("adequate foundation under accepted standards for validation" test); Id. at 27 ("' accepted standards; foundational requirement:); Id. at 27 n. 18 ("foundational rule"); Id. at 33 ("proper materials"/"used in reasonable fashion" test).
(37) Daubert, 113 S. Ct. at 2797.
(38) Id. at 2791 & n.2.
(39) FED. R EVID. 201(b).
(40) Osburn v. Anchor Lab. Inc., 825 F. 2d 908, 915 & n.10 (5th Cir. 1987), cert. denied, 485 U.S. 1009 (1988).
(41) FED. R. EVID. 201(b).
(42) Osburn, 825 F.2d at 915 & n.10. The instances in which Rule 201 (b) will permit judicial notice of adjudicative facts are relatively rare. See, e.g., Hernandez v. Denton, 861 F.2d 1421, 1426 (9th Cir. 1988) ("[t]he category of facts of which a district court may take judicial notice is a very narrow one"), vacated on other grounds, 493 U.S. 801 (1989); C.A. Hardy v. Johns-Manville Sales Corp., 681 F.2d 334, 347 (5th Cir. 1982) (judicial notice "that asbestos causes cancer" held erroneous; "judicial notice applies to self-evident truths that no reasonable person could question, truisms that approach platitudes or banalities"); Banks v. Schweiker, 654 F.2d 637, 640 (9th Cir. 1981) (Rule 201 requires "extreme caution" in "taking notice of adjudicative facts" given that "the taking of evidence, subjected to established safeguards, is the best way to resolve" adjudicative facts.
(43) Daubert, 113 S. Ct. at 2796.
(44) Id. (citing United States v. Downing, 753 F.2d 1224, 1242 (3d Cir. 1985)).
(45) Id.
(46) Id. at 2795 n.7.
