Class CertificationIntroduction:

In the first half of this year, countless groups have sought permission to litigate as members of a class action in legal proceedings, from product liability cases to employment discrimination claims. See, e.g., In re Tropicana Orange Juice Mktg. & Sales Practices Litig., No. 11-7382 (D.N.J., entered May 24, 2018); See, e.g., Michelle Chen, “The Supreme Court’s War on Class-Action Lawsuits,” The Nation, Jun. 4, 2018. Two federal cases recently upheld denials of class certification, the most recent being a Supreme Court ruling. See id.Regardless of which side a party is on, expert witnesses play an important role in class actions and class certification. This article examines litigation and provides guidance for attorneys dealing with class certification.


Class certification has long been a battle of the experts, and decisions to allow a class to proceed or deny such requests have often hinged on expert testimony. See, e.g., Terence N. Hawley & Joshua D. Anderson, “Recent Decisions Provide Ammo for Challenging Expert Testimony Supporting Class Cert,” The Recorder, Feb. 18, 2018, at For plaintiffs who wish to be certified as a class and pursue such litigation, expert witnesses can be of invaluable assistance. See, e.g., id. As two attorneys note, “Class action plaintiffs often submit expert testimony in support of class certification motions, raising the question of how defendants should respond.” Id.In federal court, the Daubert standards apply to experts when class certification is at issue. See id.

Some state courts, such as California, have somewhat similar rules to govern admissibility of expert evidence regarding class certification. See id. A 2012 California Supreme Court decision “directs the trial court to act as a gatekeeper and ensure that an expert’s opinions are not speculative and are based on, and reasonably supported by, proper data.” Id.One complication arises, however, because “as to expert evidence presented in connection with class certification motions, California state courts have arguably been less clear than their federal counterparts regarding the applicable legal standards and proper level of scrutiny.” Id.

In 2018, both the California and federal courts have become more stringent with respect to plaintiffs’ class certification motions. See id.In the wake of a series of recent appellate decisions, some legal analysts have concluded that California courts are leaning towards providing “additional legal support for rigorously analyzing and challenging expert evidence offered in support of class certification.” Id.

Both prospective plaintiffs and defendants should be aware of the federal and state trends regarding class certification. It seems likely that, due to increasing scrutiny of certification requests, plaintiffs would be well served by retaining knowledgeable experts to bolster their positions.  Defendants must be prepared to offer a counter-narrative to such experts, which may entail employing such witnesses as well.

In addition to offering competing expert testimony, parties may wish to consider how to respond to opposing witnesses. Both sides should conduct thorough discovery of one another’s experts to determine their strengths and weaknesses. Based on the particular jurisdiction a party is in, it is important to be well-acquainted with the rules governing experts in class certification matters. For instance, California is governed by the Sargonstandard, which is premised on giving trial judges a gatekeeper role and ensuring expert testimony is neither speculative nor unsupported by reasonable data. See id. If an opposing witness’s evidence does not meet those criteria, attorneys have a number of options to challenge such experts. A motion to strike adverse testimony may be appropriate, or an objection may be proper. See, e.g., id. Defendants may wish to argue that plaintiffs’ experts are unreliable under whatever standards apply to such evidence when considering class certification. See id.


It appears that federal and state courts are, on balance, moving towards more rigorous standards in approving class certification motions. Given such a trend, attorneys on both sides should be prepared to adapt to this and respond with the help of expert witnesses. For plaintiffs, retaining experts early and vetting them carefully may determine whether a class certification request is successful. For defendants, challenging plaintiffs’ experts and providing friendly witnesses with a credible counter-story may be critical. Both parties should be aware of potential pitfalls and take care to employ the best experts in the field to improve their odds.