Daubert challenges to expert testimony: Legal overview and best practices


by Jennifer Engelhardt and Chad Engelhardt   |   Michigan Bar Journal


Daubert challenges can be rife with pitfalls for the unwary practitioner or unprepared expert.1 However, by utilizing best practices, challenges can be avoided or successfully refuted.2 Moreover, by adhering to best practices, expert testimony will be stronger and more persuasive, increasing the chances of success at trial.


When litigation involves issues of disputed scientific testimony, the trial court serves as a gatekeeper to ensure that the trier of fact is informed by trustworthy evidence. Expert testimony based on scientific evidence is admissible if it is both reliable and relevant to the issues being litigated. Relevance is determined by whether the evidence “will assist the trier of fact to understand the evidence to determine a fact in issue.”3 Reliability requires that the factual basis be in evidence or subject to admission and based on “the methods and procedures of science.”4

Daubert v Merrell Down Pharmaceuticals, Inc.5 set forth several factors for judicial consideration in evaluating admissibility of scientific evidence.6 Under Daubert factors, expert opinion is admissible when supported by particular grounds for the expert’s scientific conclusion. This is true even if there are flaws in the expert’s methods or arguable grounds for alternative conclusions.7 The United States Supreme Court further clarified that an expert must “employ in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field.”8

The Michigan Legislature codified many Daubert factors when it enacted MCL 600.2955, which accounts for multiple factors in assessing the scientific reliability of an expert opinion. However, the Michigan Supreme Court in Ehler v. Misra clarified that every factor articulated in MCL 600.2955(1) need not be met in every case; rather, the relevant factors must be met.9 MRE 702 also incorporates Daubert standards of reliability as a threshold matter of admissibility.

Statutory and evidentiary Daubert factors encompassed in MCL 600.2955 and MRE 702 are frequent fodder for motion practice in tort and business litigation. The stakes are high in such disputes and failure to meet the standards can result in dismissal or severe limitations on evidence submitted to the jury.

A Daubert ruling may be dispositive but is reviewed for abuse of discretion.10 Even when not dispositive, Daubert rulings in cases centered around differing opinions from conflicting experts can substantively skew the battleground and tip the scales of justice on credibility issues. Further, Daubert hearings typically involve exhaustive evidentiary explorations and necessitate a substantial allocation of judicial time and party resources.

Daubert instructs that “[t]he focus, of course, must be solely on principles and methodology, not on the conclusions that they generate.”11 The inquiry to be undertaken by the trial court is flexible, focusing on the principles of methodology employed and not on the conclusions reached.12 An opinion grounded in facts, known scientific principles, professional experience, and application of logic is one that rests upon reliable methodology and should be admitted into evidence. All other criticisms merely go to the weight and not to the admissibility of the evidence.13 Practitioners should keep these principles in mind and avoid inviting error so the constitutional role of the jury as trier of facts and credibility is not invaded.

While Daubert challenges can occur in all varieties of tort cases, they are most prevalent in medical malpractice cases. In such cases, expert testimony is required to prove a defendant’s compliance with or deviation from the standard of care.14 Often, standard-of-care opinions are based primarily on the expert’s experience and informed by the totality of the expert’s education and training. Some of the most influential Daubert opinions have emerged from medical malpractice appellate decisions.15


An area of recent appellate focus involves the interplay of expert opinion and supportive scientific literature. The internet has changed the face of medical and scientific research. Google Scholar, databases, and subscriptions services like Pubmed, MD Consult, and UpToDate place a virtual world of scientific knowledge at our fingertips. What used to require hours or even days in a university research library searching for reference materials can be accomplished in a fraction of the time. Such searches performed early in the case — and with the assistance of analysis by your experts — can substantially strengthen the practitioner’s understanding of the issues in dispute and lead to more focused discovery and better framing of the issues at all stages of the case.

Some argue that a lack of such literature automatically renders an expert opinion scientifically unreliable and therefore ineligible for submission to the jury. Such a narrow view runs contrary to law. Lack of literature does not necessarily suggest that the expert opinion is unreliable.16 Supportive literature is a factor to be considered in evaluating the foundation of an expert opinion, but it is not the exclusive criteria.17 That is because “not every particular factual circumstance can be the subject of peer-reviewed writing. There are necessarily novel cases that raise unique facts that have not been previously discussed in the body of medical texts and journals.”18

In some circumstances, supporting scientific literature can be an important factor in determining the reliability of expert testimony.19 Industry or professional standards and learned treatises can highlight how an expert’s opinions and methodologies compare with those employed outside of litigation.


Detailed preparation for mounting or defending a Daubert challenge is paramount. Unlike trial, the rules of evidence (specifically hearsay) do not apply at Daubert hearings.20 At trial, literature may qualify as a learned treatise for purposes of impeachment when established as a reliable authority by admission, by another expert’s testimony, or by judicial notice.21

An expert must be able to explain how the facts and data have been reliably applied. An opinion is not admissible simply because an expert says so. “Nothing in either Daubert or the Federal Rules of Evidence requires a ... court to admit opinion evidence which is connected to existing data only by the ipse dixit of the expert.”22 Showing that the expert relied on principles used outside of litigation — part of the training and practice of their profession — should be emphasized, even in the absence of literature support.

Michigan courts have adopted the federal model that each (or even most) of the statutory factors which codify Daubert need not favor the proposed expert’s opinion for it to be admissible. The Elher Court acknowledged that “all the factors in MCL 600.2955 may not be relevant in every case.”23 Rather, it suffices that “the opinion is rationally derived from a sound foundation.”24 A trial court need not search for the absolute truth; that an opinion is not universally accepted or that conflicting evidence exists does not render it unreliable.25 Instead, “the proper role of the trial court is to filter out expert evidence that is unreliable, not to admit only evidence that is unassailable.”26 “[T]he fact that two scientists value the available research differently and ascribe different significance to that research does not necessarily make either of their conclusions unreliable.”27

A source of frequent confusion in medical malpractice cases is the mistaken belief that supportive literature is always required. The Michigan Supreme Court expressly held that supportive literature is not always required and “peer-reviewed, published literature is not always necessary or sufficient to meet the requirements of MRE 702.”28, 29 When assessing reliability, a lack of supporting literature combined with the lack of any other form of support can render opinion testimony unreliable.30 The Michigan Supreme Court appears poised to further clarify the role of scientific literature where a Daubert challenge has been made regarding the experiential issue of standard-of-care testimony.31


Where a Daubert challenge is foreseeable, early and detailed attorney and expert preparation can increase the likelihood of a successful outcome and potentially avoid the challenge altogether. Practitioners must understand the expert’s qualifications, methodology of review, and how an expert opinion fits into the applicable evidentiary and statutory factors within the context of the case.

An expert should be prepared to support opinion(s) using available records, images, and literature (if applicable). Detailed discussions with the expert outlining their specific education, training, and experience (including publications and teaching) are critical. Practitioners can request the expert to perform a literature search, analysis, or review when appropriate. Finding out how an expert will address Daubert factors before testifying can increase the strength and persuasion of the testimony.

Practitioners on the receiving end of a Daubert challenge should be prepared for a de facto bench trial. Consider requesting an evidentiary hearing (which is within the court’s discretion32) and have the following read where applicable:33

  • Expert CV;
  • Highlighted scientific literature (with table of contents) and, as a best practice, an abstract with excerpts of the most relevant quotes or findings and definition of key medical or scientific terms;
  • Bench brief setting forth the expert opinion, pertinent law, and pertinent facts; and
  • Any other evidence supporting the expert testimony.

Where appropriate, practitioners may wish to reference the Federal Judicial Center’s Reference Manual on Scientific Evidence34 or the Michigan Judicial Institute’s Evidence Benchbook.35


Consider inquiring about the methodology used in the field, expert qualifications, and confirmation of the scientific principles in discovery requests and depositions. Use Daubert factors as an outline for both deposition preparation and cross-examination of experts. Often, the dispute is not about the methodology used by the experts, but the conclusions they reached. That is an issue of fact to be resolved by the jury, not a matter for gatekeeping.


Daubert challenges are rightfully seen as “Death Star” issues. They are risky and resource intensive. Best practice for practitioners is identifying, analyzing, and building the foundation to support expert testimony early and soundly. Doing so will avoid many challenges and help overcome those that are made. Thorough preparation will also pay dividends in a stronger case at mediation or trial.


“Best Practices” is a regular column of the Michigan Bar Journal, edited by Gerard V. Mantese and Theresamarie Mantese for the Michigan Bar Journal Committee. To contribute an article, contact Mr. Mantese at


1. The scope and depth of this article is necessarily truncated. For a more detailed discussion complete with video, white paper, and sample pleadings, see ICLE’s On-Demand Seminar Demonstration: Daubert Hearing (March 19, 2019), available at []. All websites cited in this article were accessed May 3, 2022.

2. Engelhardt, et al, eds, Torts: Michigan Law and Practice (Ann Arbor: ICLE, 2021), which features several chapters discussing Daubert issues applied to specific fields and causes of action.

3. MRE 702.

4. MRE 703, Daubert v Merrell Dow Pharm, Inc, 509 US 579; 113 S Ct 2786; 125 L Ed 2d 469 (1993), and Gilbert v DaimlerChrysler Corp, 470 Mich 749, 781; 685 NW2d 391 (2004) (adopting Daubert standard).

5. 509 US 579; 113 S Ct 2786; 125 L Ed 2d 469 (1993) and Gilbert v Daimler­Chrysler Corp.

6. The Daubert standard was established to provide a more liberal basis compared to the standard set forth in Frye v United States, 293 F 1013 (1923), which required the proponent of scientific evidence to show that the underlying theory and tech­niques were generally accepted in the relevant scientific community.

7. Daubert, 509 US at 593.

8. Kumho Tire Co v Carmichael, 526 US 137, 152; 119 S Ct 1167; 143 L Ed 2d 238 (1999).

9. Ehler v Misra, 499 Mich 11, 27; 878 NW2d 790 (2016).

10. When the impact of a Daubert ruling is dispositive, appellate panels may use a hybrid standard of review. Michigan courts review orders for summary disposition de novo, Wright v Genessee Cp Bd of Drain Comm’rs, 504 Mich 410, 417; 934 NW2d 805 (2005). Where a question of expert witness qualification is involved, such decision is reviewed for abuse of discretion. “An abuse of discretion occurs when the trial court chooses an outcome outside the realm of reasonable and princi­pled outcomes,” Kalaj v Khan, 295 Mich App 420, 425; 820 NW2d 223 (2012). Appellate courts “review de novo questions of law underlying evidentiary rulings, in­cluding the interpretation of statutes and court rules,” Ehler v Misra, 499 Mich at 21. [A]ny error in the admission of exclusive of evidence will not warrant appellate relief unless refusal to take this action appears . . . inconsistent with substantial justice, or affects a substantial right of the [opposing] party,” Craig v Oakwood Hosp, 471 Mich 67, 76; 684 NW2d 296 (2004). See also Barnett v Hidalgo, 478 Mich 151, 159; 732 NW2d 472 (2007) (“[w]hen the trial court’s decision to admit evidence in­volves a preliminary question of law, the issue is reviewable de novo, and admitting evidence that is inadmissible as a matter of law constitutes an abuse of discretion.”)

11. Daubert, 509 US at 595.

12. Daubert, 509 US at 594.

13. E.g., Lopez v General Motors Corp, 224 Mich App 618, 632; 569 NW2d 861 (1997) and People v Stiller, 242 Mich App 38, 55; 617 NW2d 697 (2000).

14. Lince v Monson, 363 Mich 135, 108 NW2d 845 (1961).

15. E.g., Edry v Adelman, 486 Mich 634; 786 NW2d 567 (2010). See also Ehler v Misra.

16. People v Unger, 278 Mich App 210, 220; 749 NW2d 272 (2008).

17. Ehler v Misra, 499 Mich at 27. See also Robins v Garg, 276 Mich App 351; 741 NW2d 49 (2007) and Clerc v Chippewa Co War Mem Hosp, 267 Mich App 597; 705 NW2d 703 (2005).

18. Unger, 278 Mich App at 220.

19. Edry v Adelman, 486 Mich at 639-640. See also Daubert, 509 US at 593, holding that whether there is peer-reviewed and published literature on a theory is a pertinent consideration because “submission to the scrutiny of the scientific community is a component of ‘good science,’ in part because it increases the likelihood that substantive flaws in methodology will be detected.”

20. MRE 104.

21. MRE 707 and mirroring FRE 803(18).

22. General Electric Co v Joiner, 522 US 136, 146; 118 S Ct 512; 139 L Ed 2d 508 (1997).

23. Ehler v Misra, 499 Mich at 16.

24. Chapin v A & L Parts, Inc, 274 Mich App 122, 137-139; 732 NW2d 578 (2007).

25. Id. at 139.

26. People v Unger, 278 Mich App 210; 749 NW2d 272 (2008).

27. Chapin, 274 Mich App at 139.

28. Ehler v Misra, 499 Mich at 27.

29. Id. at 27-28.

30. Edry v Adelman, 486 Mich at 640 and Ehler v Misra, 499 Mich at 14.

31. Danhoff v Fahim, ____ Mich ____; 969 NW2d 71 (2022).

32. People v Unger, 278 Mich App at 216-217.

33. For a far more detailed discussion, see ICLE’s On-Demand Seminar Demonstra­tion: Daubert Hearing.

34. Available at [].

35. Available at [].