Using Experts to Strengthen Class Certification Arguments

In complex class action litigation, success at the class certification stage is often the pivotal moment that determines the trajectory of the case. Plaintiffs seeking to certify a class under Rule 23 of the Federal Rules of Civil Procedure must meet a series of exacting standards. Among these, commonality, predominance, and the existence of a viable damages model are frequently contested. Expert testimony can be essential in satisfying these requirements—offering the court a robust, data-driven foundation for certification.

Meeting Rule 23’s Commonality and Predominance Requirements

Courts no longer accept generalized allegations or superficial similarities among class members when evaluating Rule 23(a)(2)’s commonality or Rule 23(b)(3)’s predominance requirements. Following the Supreme Court’s decision in Wal-Mart Stores, Inc. v. Dukes, plaintiffs must show that class claims hinge on a common contention whose resolution will drive the case forward for all members. For predominance, as clarified in Comcast Corp. v. Behrend, the emphasis shifts to whether common questions outweigh individualized ones.

Expert testimony is indispensable in meeting these heightened standards. Economists, statisticians, and industry specialists offer the analytical tools needed to demonstrate that the defendant’s conduct had a uniform impact on the proposed class—helping establish both the existence and weight of shared legal or factual issues.

Experts may support these elements by:

• Conducting statistical analyses to reveal systemic patterns or policies affecting the class
• Examining uniform corporate practices or procedures to confirm consistent treatment
• Using data sampling techniques to extrapolate findings across a broader population
• Providing expert declarations on how a specific product defect or marketing scheme likely affected all class members in a similar way
• Evaluating whether sufficiently uniform records exist to support classwide resolution

Without such evidence, certification motions often falter under judicial scrutiny, especially where variation in class member experiences is likely.

The Role of Experts in Developing Classwide Damages Models

Rule 23(b)(3) not only requires a showing that common issues predominate—it also demands a rigorous demonstration that damages can be assessed through a consistent, classwide methodology. As Comcast reaffirmed, any proposed damages model must directly align with the plaintiffs' theory of liability. A flawed or mismatched model may be grounds for denying certification outright.

Expert economists and data scientists help satisfy this requirement by building damages models that apply uniformly across the class. These models rely on accepted economic principles and can often be applied using a shared dataset or algorithmic framework. To survive judicial scrutiny, the methodology must be both scientifically valid and tied to the underlying alleged misconduct.

Experts commonly contribute to this process by:

• Designing regression models to measure price inflation, wage loss, or economic overcharge across the class
• Applying conjoint or hedonic analysis to quantify the impact of false advertising or product misrepresentation
• Using benchmarking techniques to compare outcomes in affected versus unaffected populations
• Estimating aggregate damages based on market-wide effects or uniform misstatements
• Submitting methodologically sound declarations that connect the model to the specific harm alleged

Courts evaluating these models do not require precision at the certification stage, but they do require plausibility. Expert input ensures that the proposed method can reasonably calculate damages on a classwide basis—supporting both predominance and the overall manageability of the case.

Expert Declarations and Methodological Soundness

Courts carefully evaluate expert submissions at the class certification stage under the standards established in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993). While full merits-based scrutiny may not always be appropriate at this stage, judges do assess whether the expert’s methodology is reliable and whether it meaningfully connects to the legal theory at hand.

To that end, expert declarations should include:

• A clear explanation of the methodology and its relevance to the claims
• Identification of common data sources or policies affecting the proposed class
• An explanation of how the model can be uniformly applied to the class members

Defense attorneys will frequently challenge these declarations, arguing that assumptions are unrealistic or that models mask significant individual variation. A well-prepared expert must be able to defend the logical coherence of the methodology, even under cross-examination during evidentiary hearings. Failure to do so may result in exclusion of the testimony or rejection of certification.

Experts in Defeating Individualized Defenses

Another strategic advantage experts provide lies in neutralizing the argument that individualized defenses defeat class cohesion. For example, in cases involving deceptive advertising, defendants often assert that some consumers were not misled or suffered no injury. Experts in psychology or marketing may analyze consumer behavior to demonstrate that the advertising in question was likely to mislead a reasonable person—helping establish classwide reliance or injury.

Similarly, in product liability class actions, engineers or medical experts may examine whether a product’s design flaw would necessarily pose the same risk to all users. By showing that the defect affects all members in the same way, experts can help establish predominance even where usage patterns vary.

Strategic Use of Experts to Frame the Certification Narrative

Beyond technical analysis, experts play a vital narrative function. Their reports help frame the case around central, certifiable themes: a uniform policy, a systemic defect, a shared economic harm. Judges—particularly in borderline certification decisions—often look to the clarity and coherence of expert reports in determining whether the class should be certified.

Effective plaintiffs’ counsel will engage experts early to shape discovery, refine class definitions, and anticipate Daubert challenges. Experts who participate from the outset can craft models tailored to the facts uncovered during litigation, rather than attempting to retrofit generic methodologies to ill-suited data.

Conclusion

Class certification under Rule 23 is rarely won on legal argument alone. Courts demand rigorous evidentiary support—particularly when evaluating commonality, predominance, and damages methodologies. Expert witnesses, through their analysis and testimony, provide the indispensable foundation for these claims. When properly selected and well-prepared, experts not only satisfy procedural requirements but also persuade courts that the claims are best adjudicated on a classwide basis. In today’s litigation environment, their role is not merely helpful—it is often essential.