The global investigation into interest-rate manipulation has emboldened prosecutors to crack down on banks, and the settlement with the Royal Bank of Scotland on [Feb. 6] underscored that strategy. As part of the $612 million deal that American and British authorities reached with R.B.S., the bank's Japanese unit was required to plead guilty to criminal wrongdoing, echoing an earlier action taken against a subsidiary of UBS. The cases announced so far give other banks some idea of what to expect. Three questions come into play: how much it will cost, whether a guilty plea will be required and whether embarrassing e-mails will be released. The winners in all this may be the lawyers and other advisers. The trove of internal e-mails and employee interviews, filed as part of a lawsuit by one of the investors in the securities, offers a fresh glimpse into Wall Street's mortgage machine, which churned out billions of dollars of securities that later imploded. The documents reveal that JPMorgan, as well as two firms the bank acquired during the credit crisis, Washington Mutual and Bear Stearns, flouted quality controls and ignored problems, sometimes hiding them entirely, in a quest for profit.