Plaintiffs sued for damages under the federal antitrust laws. The district court certified a class, permitting the case to proceed on a single theory of liability. On appeal, defendants argued damages under the sole liability theory were incapable of measurement on a class-wide basis. The Third Circuit affirmed certification, but the Supreme Court reversed. Comcast Corp. v. Behrend, 133 S. Ct. 1426 (2013) (No. 11-864). The Court concluded that the damages model must measure only those damages attributable to the theory of liability presented, yet the damages testimony failed to disaggregate the damages attributable to that which made defendants’ conduct illegal. Even though the damages issue overlapped with the merits, the district court was required to assess whether damages could be calculated in a way that was common to the class. Here, the model was insufficient to determine damages on a class-wide basis and, as a result, certification was improper.