On Wednesday, the U.S. Supreme Court hears arguments in Halliburton v. Erica P. John Fund, a much anticipated case that could shape the future of securities fraud class actions.

The case may decide the fate of the 25-year-old “fraud-on-the-market” presumption, built into securities litigation, that share prices reflect the information that is available to the public. Contained in the court’s decision in Basic Inc. v. Levinson, the presumption that allows plaintiffs to sue without having to prove that individual investors read and were misled by statements made by the defendant company.