Halliburton Co. v. Erica P. John Fund, Inc.

Background

A group of investors led by Erica P. John Fund sued a company, saying the company made public false statements that inflated its stock price and later corrected them, causing investor losses. The investors asked a court to certify a class of people who bought the company's stock during the relevant period. Lower courts split over whether defendants could use evidence about causation or price effects before class certification.

Reasoning

The Court considered whether to overrule Basic, which lets investors invoke a presumption that market prices reflect public, material statements. The Court declined to overrule Basic, finding no special justification to discard it. But the Court held that defendants may present evidence at the class-certification stage showing an alleged misstatement did not actually affect the stock's market price (no "price impact"), and that such evidence can defeat the presumption before certification.

Real world impact

The decision leaves the fraud-on-the-market presumption available to plaintiffs who meet Basic's prerequisites but permits companies to try to block class treatment by proving lack of price impact early. Because the lower courts here denied that opportunity, the Supreme Court vacated the judgment and sent the case back for further proceedings. This ruling does not decide the merits of the fraud claims; it only shifts when price-impact evidence may be considered.

Dissents or concurrances

Justice Ginsburg joined the opinion. Justice Thomas (joined by two others) agreed with the judgment but wrote separately arguing that Basic should be overruled.