Should judges consider evidence that’s inadmissible at trial when deciding whether to certify a class for class‐action litigation? Particularly given the serious consequences of certification—most defendants settle class actions to avoid greater liability, and non‐certified cases are often not worth pursuing—due process should require that evidence presented at the class‐certification stage meet the same standards as that presented at trial. One case out of California illustrates how allowing inadmissible evidence in any part of a legal proceeding not only violates the due‐process rights of defendants and absent class members, but contradicts recent Supreme Court rulings and the Federal Rules of Civil Procedure. Maria del Carmen Pena is the lead plaintiff of a group of agricultural employees alleging that they were denied breaks due them under the governing law. Pena tried to gain class certification by presenting a spreadsheet summarizing work hours, but this evidence was inadmissible for trial purposes because it was created by her attorney. Nevertheless, the district court certified the class and the U.S. Court of Appeals for the Ninth Circuit affirmed. Cato has now filed a brief supporting a cert. petition, urging the Supreme Court to address just that evidentiary issue. If, as the Supreme Court recently said in Walmart Stores, Inc. v. Dukes (2011), “mere allegations” are insufficient to support certification, then it is also wrong to allow otherwise inadmissible evidence to provide the foundation for certification. Because the Court insisted in Dukes that “certification is proper only if the trial court is satisfied, after rigorous analysis, that the prerequisites of Rule 23(a) [laying out the requirements for class certification] have been satisfied,” lower courts should consider examinations of both fact and legal merits when determining if certification is appropriate. Adhering to the 1974 decision of Eisen v. Carlisle, in which the Court held that, “for purposes of determining certification, allegations made in the complaint are taken as true and the merits of the claim are not considered,” many lower courts avoid considering any issue at the certification stage that may overlap with a question on the merits—and thus have avoided requiring that evidence used to certify a class meet the normal standards for admissibility. But Dukes established that due process demands a rigorous inquiry (which sometimes may go beyond the bare pleadings) before certification. When courts accept inadmissible evidence to support class certification, the basic requirements of due process are compromised. Once certified, expenses and risks often compel settlements divorced from merit considerations; certification is, as the Eleventh Circuit has explained, “the whole ball game.” Absent class members also suffer because it is the act of certification that determines whether they are bound by a settlement or adverse judgment that wipes out their individual claims. Unfortunately, confusion over the decades‐old holding in Eisen lingers; a refusal to view it in light of the Court’s more recent decisions has resulted in an inconsistent application of evidentiary standards. The Court should take this case, dispel confusion among lower courts, and protect due‐process rights by clarifying that evidence submitted at the class‐certification stage must meet the same time‐tested standards as evidence submitted at trial.