The bank that for years helped mask the extent of Greece's deficit has been in the dock. Goldman Sachs has faced a grilling before a U.S. senate special committee. Its executives have denied any involvment in misleading their customers. The bank is accused of selling clients mortgage-backed debts on the basis they would become more valuable. Then Goldman bet these securities would fall in price - contributing to the credit crunch. The hearing is highly politicized due to Barack Obama's plan to overhaul financial rules before congressional elections in November.