Defense event-study econometrician
Expert class library · Securities · Defense side
Uses event studies to test whether alleged misstatements or corrective disclosures actually moved the stock price. Retained to rebut price impact at class certification and to challenge loss causation and damages at summary judgment and trial.
What this expert is retained to answer
- Did the alleged misstatements or corrective disclosures cause a statistically significant stock price reaction?
- Can the defendant rebut the presumption of class-wide reliance by showing the alleged fraud had no price impact?
- How much of a price decline is explained by market, industry, or other non-fraud news?
- Is the plaintiffs' event study, and the damages model built on it, reliable and consistent with the liability theory?
Methods
- Market-model event study
- Price impact rebuttal
- Multiple-comparison adjustments
- Confounding news analysis
- Intraday price analysis
How the testimony is attacked
- Inadequate control for industry movements. Plaintiffs argue the defense market model uses the wrong or too few indices, so returns that look normal would be abnormal against a better peer index. In the Halliburton remand the plaintiffs' expert claimed a peer index sharply improved the model's explanatory power.
- Multiple-comparison adjustments that hide real price reactions. When the defense adjusts significance thresholds for testing many dates, plaintiffs say the correction is too conservative and produces false negatives. The Halliburton court accepted that an adjustment was warranted but applied the less conservative Holm-Bonferroni version instead of the Bonferroni version the defense expert used.
- No price movement does not mean no price impact. Plaintiffs respond that a misstatement can maintain an already inflated price, so the absence of a price increase on the statement date proves little. In Goldman the district court repeatedly credited that inflation-maintenance theory before the Second Circuit reversed on other grounds.
- Failure to isolate the event being studied. Opponents argue an event study that does not separate the challenged event from simultaneous news is misleading. In the Fannie Mae and Freddie Mac litigation the court admitted a defense event study because the expert never claimed it isolated one part of the challenged amendment from the rest.
- Opinions that go beyond the event study. Courts examine each opinion separately, and a defense economist's add-on opinions can be excluded even when the event study survives. In the same Fannie Mae and Freddie Mac ruling the court excluded the expert's separate opinion on how a hypothetical commitment fee would have been set.
What the public record shows
A deliberately narrow CourtListener search, "price impact" AND "event study" AND (Daubert OR "Rule 702"), returned 9 opinions filed since 2015, as of October 2, 2026; broader searches return more. Three that show how courts handle this class of testimony:
| Outcome | Case | Court | Why |
|---|---|---|---|
| Admitted | Erica P. John Fund, Inc. v. Halliburton Co.309 F.R.D. 251 | N.D. Tex. 2015 | On remand from the Supreme Court, the court credited the defense expert's event study showing no price impact for all but one alleged corrective disclosure, and agreed a multiple-comparison adjustment was proper while substituting the Holm-Bonferroni method for the expert's Bonferroni method. |
| Limited | In re Fannie Mae/Freddie Mac Senior Preferred Stock Purchase Agreement Class Action LitigationsMisc. No. 2013-1288 (D.D.C. Oct. 21, 2022) | D.D.C. 2022 | The court admitted the defense expert's bond-yield event study because he did not claim it isolated one provision of the challenged amendment, but excluded his separate opinion on how a hypothetical commitment fee would have been set. |
| Admitted | Ark. Tchr. Ret. Sys. v. Goldman Sachs Grp., Inc.77 F.4th 74 | 2d Cir. 2023 | The defense experts' event studies, including evidence that dozens of earlier reports about the same conflicts did not move the stock, were part of the record on which the Second Circuit reversed class certification for lack of price impact given the mismatch between generic statements and specific corrective disclosures. |
Each case links to the free opinion text on CourtListener.
Under amended Rule 702
Since December 1, 2023, Rule 702 says expressly that the party offering an expert must show the court it is more likely than not that the testimony meets each requirement: that it rests on sufficient facts or data, uses reliable methods, and reflects a reliable application of those methods to the case. Questions about the basis of an opinion are no longer automatically matters of weight for the jury. For how the circuits have applied the amendment, see the Rule 702 tracker, which follows each court of appeals; for what that means for preparing or attacking this class of expert, see the guide on amended Rule 702.
Related classes
Guides
- Daubert Challenges to Event Studies in Securities Cases
- Price Impact at Class Certification After Goldman
- Amended Rule 702 After Nearly Three Years: What Courts Exclude
Simulating this class on a matter
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Last reviewed October 2, 2026. How this page is built: rulings are found by searching court opinions on CourtListener, and each one is read in the opinion before it is summarised here; outcomes are labelled by what the court did with the expert's testimony. No individual expert is named. This page summarises public decisions for orientation and is not legal advice; read the opinion before relying on any ruling.