Recent Supreme Court rulings have changed the landscape of what evidence may be considered by courts when deciding motions for class certification in securities litigation. This presentation provides an overview of the â€œfraud on the market theory, which permits securities-fraud plaintiffs to invoke a rebuttable presumption of reliance. We will explore the Courts recent trilogy of decisions in Haliburton I, Amgen, and Halliburton II, which require lower courts to split some very fine hairs in determining the issues relevant to class certification and those that must be reserved for the merits. The presentation will also address recent courts of appeals decisions that have provided further guidance on what a plaintiff must prove to establish, and what a defendant must prove to rebut, the fraud on the market presumption at the class certification stage. Finally, the presentation will discuss some litigation tactics that parties should consider in seeking and challenging class certification.