Class action litigation follows a distinct and outcome-defining procedural arc. Long before a case reaches trial on the merits, the dispute often turns on a central question for the parties: whether a class can be certified.
At this decisive moment, success requires more than general subject-matter expertise. It demands professionals and experts who specialize in procedural, methodological, and statistical issues governing class certification.
Cornerstone Research delivers deep, demonstrable capabilities across every phase of class action disputes. Our economic and financial consultants examine the core requirements of Rule 23, including complex evaluations of numerosity, typicality, and ascertainability, and provide rigorous empirical proof to evaluate whether common impact can be established through class-wide evidence. We help clients navigate class certification motions, conduct rapid early case assessments, and rebut plaintiffs’ allegations using data-driven methodologies that hold up to cross-examination.
By pairing deep industry knowledge with institutional data management infrastructure, we seamlessly integrate our firm-level class action expertise across all major litigation areas.
Our extensive network includes top experts from academia and industry.
Our extensive network includes top experts from academia and industry.
Mark J. Garmaise
Professor of Finance,
Joel Fried Chair in Applied Finance,
UCLA Anderson School of Management,
University of California, Los Angeles
Mark Garmaise is a corporate finance expert who specializes in topics related to banking, entrepreneurship, financial contracting, real estate, securities, and private equity (PE). Professor Garmaise has provided deposition, jury trial, and bench trial testimony, including in high-profile cases involving breach of contract claims, valuation, and damages, such as In Re Rocket Companies Inc. Stockholder Derivative Litigation.
In Rule 10b-5 securities class actions and related opt-out matters, Professor Garmaise has testified numerous times on class certification and merits issues, including market efficiency, price impact, loss causation, and damages. He provided expert testimony at the class certification stage in Shupe et al. v. Rocket Companies Inc. et al., in which the judge denied class certification.
Professor Garmaise’s industry experience includes FinTech, cryptocurrency, entertainment, financial services, investment banking, automotive, microfinance, and pharmaceuticals.
In his research, Professor Garmaise analyzes a range of complex issues affecting real estate markets, entrepreneurial firms, venture capital (VC), and PE. He has published papers on mortgage terms, the performance of small business lenders, and the effects of financial constraints on entrepreneurs. His research has appeared in peer-reviewed publications such as the Review of Financial Studies, the Journal of Finance, and the Quarterly Journal of Economics.
An award-winning instructor with more than two decades of experience, Professor Garmaise teaches M.B.A. and executive courses on corporate finance, VC, and PE (including investment strategies such as the use of special purpose acquisition companies, or SPACs).
A former senior associate dean of the M.B.A. program at the UCLA Anderson School of Management, Professor Garmaise previously served on the faculty of the University of Chicago Booth School of Business.
Our extensive network includes top experts from academia and industry.
Jennifer Marietta-Westberg
Vice President
Jennifer Marietta-Westberg is the head of Cornerstone Research’s Washington, DC, office. She also coheads the firm’s corporate and government investigations practice.
Dr. Marietta-Westberg consults on economic and financial issues arising in litigation and regulatory investigations in financial markets. She addresses allegations related to financial reporting, asset management, trading, private equity, and mergers and acquisitions (M&A).
Expert witness testimony and consulting expertise
An experienced expert witness, Dr. Marietta-Westberg has testified on matters related to Rule 10b-5/Section 11 securities class actions, the Employee Retirement Income Security Act (ERISA), general damages, valuation, alleged insider trading, alleged Ponzi schemes, spoofing, and corporate governance. Her work includes:
- Addressing class certification, loss causation, and damages issues and testifying at trial in In re Vaxart Inc. Securities Litigation, a rare securities class action trial, in which the jury returned a positive verdict for our client
- Analyzing alleged securities fraud claims in In re Kirkland Lake Gold Ltd. Securities Litigation, in which the Southern District of New York (SDNY) granted the defendants’ motion for summary judgment in its entirety, after previously denying class certification
- Opining on valuation and damages estimates in De Jaray et al. v. Lattice Semiconductor Corp., in which the jury found for the defense and denied all the plaintiffs’ claims
- Evaluating economic analyses in a civil enforcement action brought by the Commodity Futures Trading Commission (CFTC) focused on alleged spoofing in crude oil and natural gas futures markets; the CFTC agreed to dismiss the lawsuit with prejudice
- Analyzing plaintiffs’ damages claims and opposing expert opinions regarding incentive compensation in The Hertz Corporation et al. v. Frissora et al., in which the court granted summary judgment to the defense
As a senior consultant, Dr. Marietta-Westberg leads large teams to support academic and industry experts at all stages of litigation. She has worked on matters in U.S. state and federal courts, including the Delaware Court of Chancery and the SDNY.
Dr. Marietta-Westberg supported multiple experts in the first insider trading claim litigated to trial in the Delaware Chancery Court, in which Chancellor found for the defendant.
Regulatory enforcement and leadership at the SEC
Dr. Marietta-Westberg supports respondents in enforcement actions involving the Department of Justice (DOJ), the Securities and Exchange Commission (SEC), and the Commodity Futures Trading Commission (CFTC).
Dr. Marietta-Westberg worked for ten years at the SEC, in several capacities. She served as the deputy chief economist and deputy director of the Division of Economic and Risk Analysis (DERA). In these roles, she led DERA’s economic analysis in support of Commission policy and rulemaking in the areas of asset management, broker-dealers, credit rating agencies, market microstructure, and related international initiatives.
Dr. Marietta-Westberg has chaired the Investor Advisory Committee of the SEC, which offers guidance to the Commission on regulatory priorities and initiatives to support the integrity of the securities marketplace. She also served on the board of directors at the Institute for Law and Economics at the University of Pennsylvania.
Academic impact and honors for consulting excellence
Before joining the SEC, Dr. Marietta-Westberg was an assistant professor at Michigan State University, where she taught investments and statistics to undergraduates, M.B.A. students, and executives. Her research has been published in the Journal of Accounting and Economics, the Journal of Corporate Finance, and European Financial Management.
Consulting Magazine named Dr. Marietta-Westberg to its 2025 list of Women Leaders in Consulting, recognizing her for Excellence in Client Service. In addition, Women We Admire named her to its 2022 list of exceptional women leaders in Washington, DC.
Our extensive network includes top experts from academia and industry.
Justin McCrary
Paul J. Evanson Professor of Law,
Columbia Law School;
Senior Advisor, Cornerstone Research
Justin McCrary is a leading expert on statistical methods and economic modeling, with a focus on antitrust and competition, labor, and consumer product matters. Professor McCrary has testified on class certification, antitrust, labor, and statistics issues. His wide-ranging experience covers numerous industries, such as automotive, commodities, technology, healthcare, life sciences, finance, telecommunications, and retail.
Antitrust and competition
Professor McCrary testifies in complex antitrust and competition matters in various industries. His experience includes the following:
- In a significant matter in a high-tech industry, he addressed allegations of a conspiracy to fix prices and also analyzed and rebutted an opposing expert’s damages model. In another matter, he analyzed damages resulting from alleged collusion among pharmacies.
- On behalf of a global food and agriculture corporation, Professor McCrary evaluated an alleged conspiracy to manipulate wheat futures and options contracts.
- Professor McCrary has experience in multiple large and complex antitrust class actions involving financial markets. For example, he addressed statistical sampling of alleged cartel communications in In re Foreign Exchange Benchmark Rates Antitrust Litigation.
- Professor McCrary rebutted damages in a case alleging that a large software provider maintained its monopoly position through anticompetitive practices, including exclusionary contracting. The client prevailed in a confidential arbitration proceeding.
- Professor McCrary has provided testimony in antitrust matters involving intellectual property. For example, in Palm Beach Tanning Inc. et al. v. Sunless Inc., an antitrust counterclaim filed in response to a trademark case, he analyzed Section 1 and 2 tying allegations and issues related to the Robinson-Patman Act.
- In the telecommunications industry, Professor McCrary served as a consulting expert for the U.S. Department of Justice in its review of AT&T’s acquisition of T-Mobile.
Labor
Professor McCrary has wide-ranging labor markets expertise. His representative experience includes:
- In Phipps et al. v Walmart Stores Inc., one of two high-profile class action labor discrimination cases brought against Walmart, Professor McCrary provided expert analysis on the question of whether the class should be certified, analyzing Walmart’s internal wage and promotion data. Class certification was ultimately denied in both cases.
- Professor McCrary provided testimony in two seminal no-poach litigation matters involving the McDonald’s and Jimmy John’s franchises. In both matters, he analyzed the potential procompetitive benefits of the challenged clauses and opined on class certification issues. Class certification was denied in both cases, with both U.S. district court judges relying on Professor McCrary’s analyses in their opinions.
- Defense counsel retained Professor McCrary to analyze merits and damages issues in Morgan et al. v. U.S. Soccer Federation Inc., a gender pay discrimination class action. Citing Professor McCrary’s expert report in his order, the judge ruled in favor of the defendant’s motion for summary judgment.
- Defense counsel in Robinson et al. v. Jackson Hewitt Inc. and Tax Services of America retained Professor McCrary to analyze allegations that franchise no-poaching agreements restricted mobility and suppressed compensation.
Consumer fraud and product liability
Professor McCrary has testified in multiple matters alleging product liability, false advertising, and breach of contract. For example, in Beaty v. Ford Motor Company, a product liability matter involving alleged automotive defects, he provided class certification and damages rebuttal testimony.
Serving as an expert in high-profile consumer class actions, Professor McCrary has conducted empirical analyses and provided testimony on issues related to causation, liability, and damages. He has also rebutted damages models using a variety of empirical techniques, including conjoint analysis and hedonic regressions.
Statistical methods and analysis
The founding director of the Social Sciences Data Laboratory (D-Lab) at the University of California, Berkeley, Professor McCrary is an authority on high-performance computing and statistical techniques.
He has testified on sampling, probability theory, and statistical methods. In the closely watched matter In Re Twitter Inc. v. Elon Musk et al., he was retained to address allegations regarding the statistical sampling methods employed by Twitter in analyzing spam and fake accounts.
Professor McCrary has examined the statistical evidence for healthcare providers’ alleged overbilling of Medicare in both government audit and False Claims Act (FCA) matters. He also has substantial experience with mortgage-backed securities matters, including rebuttals to analyses invoking matching estimators.
Research and teaching
Professor McCrary publishes research on econometric methods, including on measuring damages in antitrust litigation. In addition, his scholarship covers a wide range of topics, including employment discrimination, high-frequency trading, financial market structure, and monetary policy. A prolific author and coauthor, his work has appeared in leading journals, including the American Economic Review, the Journal of Econometrics, and the Review of Economics and Statistics. Professor McCrary is a faculty research associate at the National Bureau of Economic Research (NBER).
Before joining Columbia University, Professor McCrary taught at the School of Law at the University of California, Berkeley.
Our extensive network includes top experts from academia and industry.
Lorin M. Hitt
Zhang Jindong Professor of Operations, Information and Decisions,
The Wharton School, University of Pennsylvania;
Senior Advisor, Cornerstone Research
Lorin Hitt is an expert in applied econometrics who works on a broad range of antitrust, product liability, and intellectual property matters. He studies the role of information and information technology in pricing and product strategy decisions, competition, market structure, and consumer behavior.
Professor Hitt’s research focuses on how information and technology create economic value; how goods and services are priced; how competition works in information-intensive industries and online markets; and how consumers search and use information in their decision-making, among other topics. In his research, Professor Hitt utilizes a variety of empirical methods to estimate demand and supply, measure the effect of external events on market prices, and value individual product features in differentiated products.
Professor Hitt has substantial experience addressing class certification, damages, and liability issues. His expertise includes analyzing market data and evaluating proposed empirical methods such as hedonic price analyses, difference-in-differences regression analyses, and conjoint analyses. He has testified in high-profile antitrust, product liability, data privacy, data breach, and intellectual property matters, such as:
- Epic v. Apple, a matter involving Apple’s App Store, which Global Competition Review (GCR) recognized as its 2022 Matter of the Year and Litigation of the Year – Non-Cartel Defence
- Earl et al. v. Boeing and Southwest, in which the Fifth Circuit de-certified the proposed class on appeal
- Volkswagen “Clean Diesel” Litigation (Nemet et al. v. Volkswagen), in which the judge dismissed the case, finding the plaintiffs’ analyses to be unreliable and inadmissible due to critical flaws that Professor Hitt identified
- Johannessohn et al. v. Polaris Industries Inc.
- In Re TFT-LCD (Flat Panel) Antitrust Litigation
- Stragent LLC et al. v. Intel Corp.
Professor Hitt’s research has been published in leading economics and management journals, including the Quarterly Journal of Economics, the Review of Economics and Statistics, the Journal of Economic Perspectives, Brookings Papers on Economic Activity, Management Science, and Information Systems Research.
At the Wharton School and the Massachusetts Institute of Technology, Professor Hitt has taught courses on competition and customer pricing, information systems management, the economics of technology, and data analysis. He has won the annual Wharton Undergraduate Teaching Award more than ten times, and he has also been honored with the Wharton-wide Hauck Award and the University of Pennsylvania-wide Lindback Award for distinguished teaching.
Class Certification Capabilities
Our firm is a recognized leader in economic and financial consulting for complex securities disputes. We bring highly differentiated experience to Rule 10b-5 cases and Section 11 and Section 12 class actions.
Landmark successes showcase our prowess at supporting clients at the class certification stage. We provide comprehensive support for financial economists, industry experts, and other experts to rigorously address issues such as market efficiency, price impact, and potential damages methodologies. Examples of pivotal decisions at class certification in which we have provided support include:
Defeating class certification in antitrust matters requires a focused look at market dynamics and individual transaction data.
We have worked on many direct and indirect purchaser class certification matters. Our case experience and analytical breadth enable us to meet the changing demand for rigorous empirical and conceptual assessment of both the questions of common impact and common proof and of the merits issues that bear on those questions.
Our experts have experience challenging plaintiffs’ proposed class-wide formulas and exposing customer heterogeneity that can defeat uniform treatment. Recently, we have assisted counsel in antitrust matters involving mobile devices, pharmaceuticals, and employment practices.
Cornerstone provides class certification analyses in a wide range of healthcare cases, including antitrust and competition, managed care contracting, coverage disputes, reimbursement practices, and disputes related to alleged “surcharge fees” and “surprise medical billing.” Clients also seek our expertise in class certification analyses for cases involving claims of product liability, misrepresentation, and false advertising pertaining to medical coverage, healthcare benefits, and other healthcare products. We have addressed questions of common proof and common impact as well as questions of ascertainability and numerosity.
In addressing these questions, we combine our extensive knowledge of the complexities and unique characteristics of the healthcare markets (including pricing and payment complexity, patient heterogeneity, and provider-payor interactions) and our expertise with advanced empirical and statistical techniques.
Cornerstone’s professionals and experts conduct extensive research and have a granular knowledge of the institutions and regulations that govern biopharmaceutical competition. We have addressed class certification in a wide range of matters, with our experience including economic analysis of alleged price fixing and market allocation; delayed generic entry, by means of reverse payments (“pay-for-delay”); and anticompetitive rebate bundling.
The class certification stage of consumer class actions often turns on the particulars of the challenged conduct, the overall structure of the industry and the market, and the characteristics of individual transactions. We evaluate these issues through empirical research within a framework of sound economic concepts, helping clients show that individualized inquiries may outweigh common questions.
- The benefit of the bargain harm: Where plaintiffs claim that consumers would have paid less or foregone the purchase entirely had they not been allegedly misled by labeling, advertising, or disclosures.
- Diminished resale value: Assessing the alleged long-term economic impact on durable goods due to the challenged conduct.
- Demand and price inflation claims: Testing plaintiffs’ arguments that an alleged conduct caused automated, class-wide impact, even for consumers uninfluenced by the marketing.
We work with some of the largest providers of consumer finance products in class action matters involving mortgage and appraisal services, credit card products, student loans, subprime and other loans, credit reporting practices, and collection practices. For client matters that involve issues of customer understanding and expectations, our experts and staff use sophisticated tools of economic analysis to model consumer behavior to rebut commonality at the class certification stage.
Class certification issues are central to complex discrimination and labor market antitrust matters. Working with leading academic experts, Cornerstone applies advanced statistical methods to assess whether common impact can be established using common class-wide evidence and methodologies. We process and analyze massive corporate datasets for wage-and-hour disputes and systemic discrimination cases.
Our statistical assessments examine independent variables to determine whether alleged workplace disparities are truly systemic or the result of localized decision-making. Our experience spans a wide range of labor market skill levels and industries—including retail, fast food, manufacturing, technology, sports, finance, and healthcare. Notable high-profile labor matters featuring our class certification phase analysis include Dukes v. Walmart and Phipps v. Walmart.
Our professionals and experts have deep experience at the class certification stage of ERISA matters. We routinely address issues including conflicts of interest, named plaintiff standing, and challenges in calculating class-wide damages. Work in these cases often involves analysis of large-scale, individual-level transaction datasets to calculate individual-level investment performance in challenged funds or recordkeeping fee charges.
Our firm has extensive experience supporting parties across the full spectrum of collective and group redress proceedings in both the UK and the European Union. In the UK, we have advised on matters before the Competition Appeal Tribunal, including the certification stage of Collective Proceedings Orders (CPOs), where economic analysis plays a critical role in demonstrating suitability for collective action. We also bring hands-on experience with Group Litigation Orders (GLOs) in the High Court, supporting clients through the establishment of the group register and the procedural steps that follow.
Our expertise extends to representative actions under CPR 19.8, where we assist in assessing whether proposed class members share the “same interest”—a threshold question with significant economic dimensions. Across the EU, we have supported clients in the admissibility and standing verification stages of representative actions, navigating the requirements that determine whether a claim may proceed on behalf of a defined group.
Together, this breadth of experience across jurisdictions and procedural stages enables us to provide robust economic analysis at the moments that matter most in complex litigation.
At the earliest stage of a class dispute, clients need financial and economic professionals who can ground or dismantle class-wide assertions with clear, empirical data.
To help clients address the shifting demands of modern legal technology, Cornerstone pairs deep industry knowledge with institutional data management infrastructure, delivering clearer outcomes:
- Large, Complex Databases: We build and manage massive, individual-level transaction datasets, cleaning and structuring raw corporate data for litigation readiness.
- Advanced Statistical Methods: Our experts go beyond basic linear modeling, using simulations, archival analysis, and test/control experiments to deliver clear insights.
- Cutting-Edge Technology: We leverage these tools to conduct rapid, large-scale reviews of corporate disclosures, communications, and public filings to assess consistency across class groups.
Featured Cases
Selected Professionals
Our professionals contribute expertise in economics, finance, accounting, and marketing, as well as business acumen, familiarity with the litigation process, and a commitment to provide outstanding support.
- Sara E. Gilley
Sara E. Gilley
Senior Vice President
- Jennifer McCabe
Jennifer McCabe
Senior Vice President
- Celeste C. Saravia
Celeste C. Saravia
Vice President