Discovery of Retained, Testifying Statistician Expert Witnesses (Part 2)

Discovery Beyond the Report and the Deposition

The lesson of the cases interpreting Rule 26 is that counsel cannot count exclusively upon the report and automatic disclosure requirements to obtain the materials necessary or helpful for cross-examination of statisticians who have created their own analyses. Sometimes just asking nicely suffices[1]. Other avenues of discovery are available, however, for reluctant disclosers. In particular, Rule 26(b) authorizes discovery substantially broader than what is required for inclusion in an expert witness’s report.

Occasionally, counsel cite caselaw that has been superseded by the steady expansion of Rule 26[2]. The 1993 amendments made clear, however, that Rule 26 sets out mandatory minimum requirements that do not define or exhaust the available discovery tools to obtain information from expert witnesses[3]. Some courts continue to insist that a party make a showing of necessity to go beyond the minimal requirements of Rule 26[4], although the better reasoned cases take a more expansive view of the proper scope of expert witness discovery[5].

Although the federal rules may not require the expert witness report to include, or to attach, all “working notes or recordings,” or calculations, alternative analyses, and data output files, these materials may be the subject of proper document requests to the adverse party or perhaps subpoenas to the expert witness.  The Advisory Committee Notes explain that the various techniques of discovery kick in by virtue of Rule 26(b), where automatic disclosure and report requirements of Rule 26(a) leave off:

“Rules 26(b)(4)(B) and (C) do not impede discovery about the opinions to be offered by the expert or the development, foundation, or basis of those opinions. For example, the expert’s testing of material involved in litigation, and notes of any such testing, would not be exempted from discovery by this rule. Similarly, inquiry about communications the expert had with anyone other than the party’s counsel about the opinions expressed is unaffected by the rule. Counsel are also free to question expert witnesses about alternative analyses, testing methods, or approaches to the issues on which they are testifying, whether or not the expert considered them in forming the opinions expressed. These discovery changes therefore do not affect the gatekeeping functions called for by Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), and related cases.[6]

The court in Ladd Furniture v. Ernst & Young explained the structure of Rule 26 with respect to underlying documents, calculations, and data[7].  In particular, the requirements of the Rule 26(a) report do not create a limitation on Rule 26(b) discovery:

“As a basis for withholding the above information, Ladd argues that Ernst & Young is not entitled to discover any expert witness information which is not specifically mentioned in Rule 26(a)(2)(B). However, as explained below, Ladd’s position on this point is not supported by the text of Rule 26 or by the Advisory Committee’s commentary to Rule 26(a). In the text, Rule 26(a)(2)(B) provides for the mandatory disclosure of certain expert witness information, even without a request from the opposing party. However, there is no indication on the face of the rule to suggest that a party is absolutely prohibited from seeking any additional information about an opponent’s expert witnesses. In fact, Rule 26(b)(1) describes the scope of allowable discovery as follows: ‛Parties may obtain discovery regarding any matter, not privileged, which is relevant to the subject matter involved in the pending action… .’ Fed. R. Civ. P. 26(b)(1).[8]

Expert witness discovery for materials that go beyond what is required in an adequate Rule 26(a) report can have serious consequences for the expert witness who fails to produce the requested materials. Opinion exclusion is an appropriate remedy against an expert witness who failed to keep data samples and statistical packages because the adversary party “could not attempt to validate [the expert witness’s] methods even if [the witness] could specifically say what he considered.[9]

No doubt expert witnesses and parties will attempt to resist the call for working notes and underlying materials on the theory that the requested documents and materials are “draft reports,” which are now protected by the revisions to Rule 26.  For the most part, these evasions have been rejected[10].  In one case, for instance, in which an expert witness’s assistants compiled and summarized information from individual case files, the court rejected the characterization of the information as part of a “draft report,” and ordered their production.[11]

Choice of Discovery Method Beyond Rule 26 Automatic Disclosure

In addition to the mandatory expert report and disclosure of data and facts, and the optional deposition by oral examination, parties have other avenues to pursue discovery of information, facts, and data, from expert witnesses. Under Rule 33(a)(2), parties may propound contention interrogatories that address expert witnesses’ opinions and conclusions. As for methods of discovery beyond what is discussed specifically in Rule 26, courts are confronted with a threshold question whether Rule 34 requests to produce, Rule 30(b)(2) depositions by oral examination, or Rule 45 subpoenas are the appropriate discovery method for obtaining documents from a retained, testifying expert witness. In the view of some courts, the resolution to this threshold question turns on whether expert witnesses are within the control of parties such that parties must respond to discovery for information, documents, and things within the custody, possession, and control of their expert witnesses.

Subpoenas Are Improper

Some federal district courts view Rule 45 subpoenas as inappropriate discovery tools for parties[12] and persons under the control of parties. In Alper v. United States[13], the district court refused to enforce plaintiff’s Rule 45 subpoena that sought documents from defendant’s expert witness. Although acknowledging that Rule 45’s language was unclear, the Alper court insisted that since a party proffers an expert witness, that witness should be considered under the party’s control[14]. And because the expert witness was “within defendant’s control,” the court noted that Rule 34 rather than Rule 45 governed the requested discovery[15]. Alper seems to be a minority view, but its approach is attractive in streamlining discovery, eliminating subpoena service issues for expert witnesses who may live outside the district, and forcing the sponsoring party to respond and to obtain compliance with its retained expert witness.

Subpoenas Are Proper

The “control” rationale of the Alper case is questionable. Rule 45 contains no statement of limitation to non-parties[16]. Parties “proffer” fact witnesses, but their proffers do not restrict the availability of Rule 45 subpoenas. More important, expert witnesses are not truly under the control of the retaining parties. Expert witnesses have independent duties to the court, and under their own professional standards, to give their own independent opinions[17].

Many courts allow discovery of expert witness documents and information by Rule 45 subpoena on either the theory that Rule 45 subpoenas are available for both parties and non-parties or the theory that expert witnesses are sufficiently independent of the sponsoring party that they are non-parties who are clearly subject to Rule 45. If expert witnesses are not parties, and Rule 26’s confidentiality provisions do not constrain the available discovery tools for expert witnesses, then expert witness subpoenas would appear to a proper discovery tool to discover documents in the witnesses’ possession, control, and custody[18]. When used as a discovery tool in this way, subpoenas used are subject to discovery deadlines[19].

Particular Concerns for Discovery of Statistician Expert Witnesses

Statistician expert witnesses require additional care and discovery investigation in complex products liability cases[20].  The caselaw sometimes takes a crabbed approach that refuses to provide parties access to their adversaries’ statistical analyses, calculations, data input  and output files, and graphical files.

Statistician expert testimony will usually involve complex statistical evidence, models, assumptions, and calculations. These materials will in turn create a difficulty in discerning the statistician’s choices from available statistical tests, and whether the statistician exploited the opportunity for multiple tests to be conducted serially with varying assumptions until a propitious result was obtained. Given these typical circumstances, statistical expert witness testimony will almost always require full disclosure to allow the adversary a fair opportunity to cross-examine at trial, or to challenge the validity of the proffered analyses under Rules 702 and 703[21].

Statisticians create and use a variety of materials that are clearly relevant to the their opinion:

  • programs and programming code run to generate all specified analyses on specified data,
  • statistical packages,
  • all data available,
  • all data “cleaning” or data selection processes,
  • selection of variables from those available,
  • data frames that show what data were included (and excluded) in the analyses,
  • data input files,
  • all specified tests run on all data,
  • all data and analysis output files that show all analyses generated,
  • all statistical test diagnostics and tests of underlying assumptions, and
  • graphical output files.

The statistician may have made any number of decisions or judgments in selecting which statistical test results to incorporate into his or her final report.  The report will in all likelihood not include important materials that would allow another statistician to fully understand, test, replicate, and criticize the more conclusory analysis and statements in the report.  In addition, lurking in the witnesses files, or in the electronic “trash bin” may be alternative analyses that were run and discarded, and not included in the final report.  Why and how those alternative analyses were run but discarded, may raise important credibility or validity questions, as well as provide insight into the statistician’s analytical process, all important considerations in preparing for cross-examination and rebuttal.  The lesson of Rule 26, and the caselaw interpreting its provisions, is that lawyers must make specific request for the materials described above.  Only with these materials firmly in hand, can a deposition fully explore the results obtained, the methods used, the assumptions made, the assumptions violated, the alternative methods rejected, the data used, the data available, data not used, the data-dredging and manipulation potential, analytical problems, and the potential failure to reconcile inconsistent results. Waiting for trial, or even for the deposition, may well be too late[22].

The warrant for examining the integrity of data relied upon by expert witnesses appears to be securely embedded in the Federal Rules of Civil Procedure, and in the Federal Rules of Evidence. Evidence Rule 703 has particular relevance to statistical or epidemiologic testimony. Lawyers facing studies of dubious quality may need to press for discovery of underlying data and materials. In the Viagra vision loss multi-district litigation (MDL), the defendant sought and obtained discovery of underlying data from plaintiffs’ expert witness’s epidemiologic study of vision loss among patients using Viagra and similar medications[23]. Although the Viagra MDL court had struggled with inferential statistics in its first approach to defendant’s Rule 702 motion, the court understood the challenge based upon lack of data integrity, and reconsidered and granted defendant’s motion to exclude the challenged expert witness[24].

The lawyering implications for discovery of statistician expert witnesses are important. Statistical evidence requires counsel’s special scrutiny to ensure compliance with the disclosure requirements of Federal Rule of Civil Procedure 26. Given the restrictive reading of Rule 26 by some courts, counsel will need to anticipate the use of other discovery tools. Lawyers should request by Rule 34 or Rule 45, all computer runs, programming routines, and outputs, and they should zealously pursue witnesses’ failure to maintain and produce data. Given the uncertainty in some districts whether expert witnesses are subject to subpoenas, counsel may consider propounding both Rule 34 requests and serving Rule 45 subpoenas.

Lawyers in data-intensive cases should give early consideration to appropriate discovery plans that contemplate data production in advance of depositions, to allow full exploration of analyses at deposition[25]. Lawyers should also be alert to the potential need to show particularized need for the requested data and analyses. In instructing expert witnesses on their preparation of their reports, lawyers should consider directing their expert witnesses to express whether they need further access to the adversary’s expert witnesses’ underlying data and materials to fully evaluate the proffered opinions. Discovery of statisticians and their data and their analyses requires careful planning, as well as patient efforts to educate the court about the need for full exploration of all data and all analyses conducted, whether or not incorporated into the Rule 26 report.


[1] Randall v. Rolls-Royce Corp., 2010 U.S. Dist. LEXIS 23421, *4-5 (S.D. Ind. March 12, 2010) (“Dr. Harnett who began his evaluation of the analysis contained in the report … soon concluded that he needed the underlying studies and statistical programs created or used by Dr. Drogin. In response to the Defendants’ request for such materials, Plaintiffs produced four discs containing more than 1,000 separate electronic files”).

[2] Marsh v. Jackson, 141 F.R.D. 431, 432–33 (W.D. Va. 1992) (holding that Rule 45 could not be used to obtain an opposing expert’s files because Rule 26(b)(4) limits expert discovery to depositions and interrogatories as a policy matter)

[3] See Advisory Comm. Notes for 1993 Amendments, to Fed. R. Civ. P. 26(a) (“The enumeration in Rule 26(a) of items to be disclosed does not prevent a court from requiring by order or local rule that the parties disclose additional information without a discovery request. Nor are parties precluded from using traditional discovery methods to obtain further information regarding these matters, … .”); United States v. Bazaarvoice, Inc., C 13-00133 WHO (LB), 2013 WL 3784240 (N.D. Cal. July 18, 2013) (“Rule 26(a)(2)(B) . . . does not preclude parties from obtaining further information through ordinary discovery tools”) (internal citations omitted).

[4] Morriss v. BNSF Ry. Co., No. 8:13CV24, 2014 WL 128393, at *4–6, 2014 U.S. Dist. LEXIS 3757, at *17 (D.Neb. Jan. 13, 2014) (holding that “absent some threshold showing of “compelling reason,” the broad discovery provisions of Rules 34 and 45 cannot be used to undermine the specific expert witness discovery rules in Rule 26(a)(2)”).

[5] Modjeska v. United Parcel Service Inc., No. 12–C–1020, 2014 WL 2807531 (E.D. Wis. June 19, 2014) (holding that Rule 26(a)(2)(B) governs only disclosure in expert witness reports and does not limit or preclude further discovery using ordinary discovery such as requests to produce); Expeditors Int’l of Wash., Inc. v. Vastera, Inc., No. 04 C 0321, 2004 WL 406999, at *3 (N.D. Ill. Feb.26, 2004). See also Wright & Miller, 9A Federal Practice & Procedure Civ. § 2452 (3d ed. 2013).

[6] Adv. Comm. Note for Rule 26(b)(4)(B)(2010).  See, e.g., Ladd Furniture v. Ernst & Young, 1998 U.S. Dist. LEXIS 17345, at *34-37 (M.D.N.C. Aug. 27, 1998).

[7] Id.

[8] Id. at *36-37.

[9] Innis Arden Golf Club v. Pitney Bowes, Inc., 629 F. Supp. 2d 175, 190 (D. Conn. 2009) (excluding expert opinion because his samples and data packages no longer existed and thus “[d]efendants could not attempt to validate [his] methods even if he could specifically say what he considered”). See also Jung v. Neschis, No. 01–Civ. 6993(RMB)(THK), 2007 WL 5256966, at *8–15 (S.D.N.Y. Oct. 23, 2007) (finding that a party’s failure to produce tape recordings that its medical expert witness relied upon for his opinion was ‘‘disturbing’’; precluding expert witness’s testimony).

[10] See, e.g., Dongguk Univ. v. Yale Univ., No. 3:08-CV-00441, 2011 WL 1935865, at *1 (D. Conn. May 19, 2011) (holding that “an expert’s handwritten notes are not protected from disclosure because they are neither drafts of an expert report nor communications between the party’s attorney and the expert witness”).

[11] D.G. ex rel. G. v. Henry, No. 08-CV-74-GKF-FHM, 2011 WL 1344200, at *1 (N.D. Okla. Apr. 8, 2011) (ordering production of the assistants’ notes because the expert witness had relied upon them in forming his opinion, which brought them within the scope of “facts or data” under the rule).

[12] Mortgage Info. Servs, Inc. v. Kitchens, 210 F.R.D. 562, 564-68 (W.D.N.C. 2002) (holding that nothing in Rule 45 precludes its use on a party); See also Mezu v. Morgan State Univ., 269 F.R.D. 565, 581 (D. Md. 2010) (“courts are divided as to whether Rule 45 subpoenas should be served on parties”); Peyton v. Burdick, 2008 U.S. Dist. LEXIS 106910 (E.D. Cal. 2008) (discussing the split among courts on the issue).

[13] 190 F.R.D. 281 (D. Mass. 2000).

[14] Id. at 283.

[15] Id. See Ambrose v. Southworth Products Corp., No. CIV.A. 95–0048–H, 1997 WL 470359, 1 (W.D. Va. June 24, 1997) (holding a “naked” subpoena duces tecum directed to a non-party expert retained by a party is not within the ambit of a Rule 45 document production subpoena, and not permitted by Fed. R. Civ. Pro. 26(b)(4)); see also Hartford Fire Ins. v. Pure Air on the Lake Ltd., 154 F.R.D. 202, 208 (N.D. Ind. 1993) (holding a party cannot use Rule 45 to circumvent Rule 26(b)(4) as a method to obtain an expert witness’s files); Marsh v. Jackson, 141 F.R.D. 431, 432 (W.D. Va. 1992) (noting that subpoena for production of documents directed to non-party expert retained by a party is not within ambit of Fed. Rule 45(c)(3)(8)(ii)).

[16] See James Wm. Moore, 9 Moore’s Federal Practice § 45.03[1] (noting that “[s]ubpoenas under Rule 45 may be issued to parties or non-parties”).

[17] See Glendale Fed. Bank, FSB v.United States, 39 Fed. Cl. 422, 424 (Fed. Cl. 1997) (“The expert witness, testifying under oath, is expected to give his own honest, independent opinion… He is not the sponsoring party’s agent at any time merely because he is retained as its expert witness”). See also National Justice Compania Naviera S.A. v. Prudential Assurance Co. Ltd., (“The Ikarian Reefer”), [1993] 2 Lloyd’s Rep. 68 at 81-82 (Q.B.D.), rev’d on other grounds [1995] 1 Lloyd’s Rep. 455 at 496 (C.A.) (embracing the enumeration of duties, including a duty to “provide independent assistance to the Court by way of objective unbiased opinion in relation to matters within his expertise,” and a duty to eschew “the role of an advocate”).

[18] Western Res., Inc. v. Union Pac. RR, No. 00-2043-CM, 2002 WL 1822428, at *3 (D. Kan. July 23, 2002) (ordering expert witness to produce prior testimony under Rule 45); All W. Supply Co. v. Hill’s Pet Prods. Div., Colgate-Palmolive Co., 152 F.R.D. 634, 639 (D. Kan. 1993) (“With regard to nonparties such as plaintiff’s expert witness, a request for documents may be made by subpoena duces tecum pursuant to Rule 45”); Smith v. Transducer Technology, Inc., No. Civ. 1995/28, 2000 WL 1717332, 2 (D.V.I. Nov. 16, 2000) (holding that Rule 30(b)(5) deposition notice, served upon opposing party, is not an appropriate discovery tool to compel expert witness to produce documents from at his deposition) (noting that a “Rule 45 subpoena duces tecum in conjunction with a properly noticed deposition may do so (subject however to any Rule 26 limitations)”); Thomas v. Marina Assocs., 202 F.R.D. 433, 434 (E.D. Pa. 2001) (denying motion to quash subpoenas issued to party’s expert witness); Quaile v. Carol Cable Co., Civ. A. No. 90-7415, 1992 WL 277981, at *2 (E.D. Pa. Oct. 5, 1992) (granting motion to compel discovery concerning expert witness’s opinions pursuant to a Rule 45 subpoena); Lawrence E. Jaffe Pension Plan v. Household Int’l, Inc., No. 02 C 5893, 2008 WL 687220, at *2 (N.D. Ill Mar. 10, 2008) (“It is clear . . . that a subpoena duces tecum . . . is an appropriate discovery mechanism against . . . a party’s expert witness”) (internal citation omitted); Expeditors Internat’l of Wash., Inc. v. Vastera, Inc., No. 04 C 0321, 2004 WL 406999, at *2-3 (N.D. Ill. Feb. 26, 2004) (holding Rule 45, not Rule 34, governs discovery from retained experts) (“Subpoena duces tecum is . . . an appropriate discovery mechanism against nonparties such as a party’s expert witness”); Reit v. Post Prop., Inc., No. 09 Civ. 5455(RMB)(KNF), 2010 WL 4537044, at *9 (S.D.N.Y. Nov. 4, 2010) (“Subpoena duces tecum … is an appropriate discovery mechanism against a nonparty expert”).

[19] See, e.g., Williamson v. Horizon Lines LLC , 248 F.R.D. 79, 83 (D. Me. 2008) (“[C]ontrary to Horizon Lines’ contention, there is a relationship between Rule 26 and Rule 45 and parties should not be allowed to employ a subpoena after a discovery deadline to obtain materials from third parties that could have been produced before discovery.”).

[20] Bartley v. Isuzu Motors Ltd., 151 F.R.D. 659, 660-61 (D. Colo. 1993) (ordering party to create and preserve “the input and output data for each variable in the program, for each iteration, or each simulation,” as well as a record of all simulations performed, even those that do not conform to the plaintiff’s claims and theories in the case).

[21] See City of Cleveland v. Cleveland Elec. Illuminating Co., 538 F. Supp. 1257 (N.D. Ohio 1980) (“Certainly, where, as here, the expert reports are predicated upon complex data, calculations and computer simulations which are neither discernible nor deducible from the written reports themselves, disclosure thereof is essential to the facilitation of effective and efficient examination of these experts at trial.”); Shu-Tao Lin v. McDonnell-Douglas, Corp., 574 F. Supp. 1407, 1412-13 (S.D.N.Y. 1983) (granting new trial, and holding that expert witness’s failure to disclosure the “nature of [the plaintiff’s testifying expert’s] computer program or the underlying data, the inputs and outputs employed in the program” deprived adversary of an “adequate basis on which to cross-examine plaintiff’s experts”), rev’d on other grounds, 742 F.2d 45 (2d Cir. 1984).

[22] Manual for Complex Litigation at 99, § 11.482 (4th ed. 2004) (“Early and full disclosure of expert evidence can help define and narrow issues. Although experts often seem hopelessly at odds, revealing the assumptions and underlying data on which they have relied in reaching their opinions often makes the bases for their differences clearer and enables substantial simplification of the issues. In addition, disclosure can facilitate rulings well in advance of trial on objections to the qualifications of an expert, the relevance and reliability of opinions to be offered, and the reasonableness of reliance on particular data.207”). See also ABA Section of Antitrust Law, Econometrics: Legal, Practical, and Technical Issues at 75-76 (2005) (advising of the necessity to obtain all data, all analyses, and all supporting materials, in advance of deposition to ensure efficient and effective discovery procedures).

[23] In re Viagra Prods. Liab. Litig., 572 F. Supp. 2d 1071, 1090 (D. Minn. 2008).

[24] In re Viagra Prods. Liab. Litig., 658 F. Supp. 2d 936, 945 (D. Minn. 2009).

[25] See Fed. R. Civ. Pro. 16(b); 26(f).

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