In Erica P. John Fund, Inc. v. Halliburton, No. 12-10544 (5th Cir. Apr. 30, 2013), plaintiffs alleged that Halliburton made misrepresentations by understating its projected liabilities and overstating its revenues, and exaggerated the efficiencies the company would derive from a 1998 merger, all of which allegedly inflated the stock price until the truth was revealed. The plaintiffs originally moved for class certification in September 2007. The district court conducted a limited inquiry under Rule 23(b)(3) and found that plaintiffs had not made a showing of loss causation. The Fifth Circuit affirmed, but the Supreme Court reversed in June 2011, finding that proof of loss causation is not required for class certification. On remand, Halliburton argued to the district court that the class should still not be certified. Halliburton offered evidence of price impact to rebut the fraud-on-the-market presumption of reliance. The Supreme Court has held that defendants can rebut some elements of the presumption at class certification, but not others. Halliburton offered price impact evidence to demonstrate not that a particular element of the presumption was not met, but that overall, the market price did not incorporate fraudulent information. The district court declined to consider the company’s evidence on the issue, finding that price impact did not bear on whether common issues predominated, and went on to certify the class, which Halliburton appealed to the Fifth Circuit. The Fifth Circuit held that price impact evidence inherently applies to everyone in the class, suggesting that it should not be addressed at class certification. The court further held that there was no risk that a later failure of proof of price impact would result in individual issues predominating, because plaintiffs must prevail on the issue of price impact in order to succeed on the merits, since it is also an element of loss causation. Thus, the question did not go to whether common issues predominate, and the lower court was affirmed.