On June 23, the U.S. Supreme Court rejected a challenge to the long-standing “fraud-on-the-market” theory, on which securities class actions often are based. Halliburton v. Erica P. John Fund Inc., No. 13-317, 2014 WL 2807181 (Jun. 23, 2014). Halliburton petitioned the Court after an appeals court relied on the theory to affirm class certification in a securities suit against the company, even after the appeals court acknowledged that no company misrepresentation affected its stock price. The theory at issue derives from the Court’s holding in Basic Inc. v. Levinson, 485 U.S. 224 (1988) that a putative class of investors should not be required to prove that each individual actually relied in common on a misrepresentation in order to obtain class certification and prevail on the merits. The petitioner argued that empirical evidence no longer supports the economic theory underlying the Court’s holding in Basic allowing putative class members to invoke a classwide presumption of reliance based on the concept that all investors relied on the misrepresentations when they purchased stock at a price distorted by those misrepresentations. The Court declined to upset the precedent set in Basic, holding that the petitioner failed to show a “special justification” for overruling presumption of reliance because petitioner had failed to establish a fundamental shift in economic theory and that Basic’s presumption is not inconsistent with more recent rulings from the Court. The Court also declined to require plaintiffs to prove price impact directly at the class certification stage, but agreed with the petitioner that a defendant may rebut the presumption and prevent class certification by introducing evidence that the alleged misrepresentations did not distort the market price of its stock.