A multibillion-dollar fraud at Colonial Bank was so well-concealed that nobody found it—not internal auditors, outside accountants or federal and state regulators, a defense lawyer for PricewaterhouseCoopers said in the opening statements of a negligent auditing trial Tuesday.

PwC complied with standards in its yearly audits of Colonial Bank’s parent company, argued Beth Tanis of King & Spalding in Atlanta. Collusion among criminals at the bank and at its largest customer, Taylor Bean & Whitaker Mortgage Corp., kept the fraud hidden from everyone until a bank employee came forward to the FBI.