Bernard Madoff has taken steps that suggest he could plead guilty as early as next week to charges that he carried out one of the biggest financial frauds in history, lawyers said Friday. Madoff, 70, is waiving his right to have a grand jury hear the government's case against him, agreeing instead to be charged directly by prosecutors, a step defendants take when they are preparing to plead guilty in a case. It is unclear when a possible plea deal could occur, and negotiations could still fall apart. Madoff has a hearing in Manhattan federal court scheduled for next week that could serve as the venue for a guilty plea. A potential plea deal could mark an important step toward answering the vexing questions about how Madoff carried out his sweeping scheme and who else may have been involved in a fraud that has wiped out investors' life savings around the world.