Even now that prosecutors are examining repeat offenses on Wall Street, they are likely to seek punishments more symbolic than sweeping. Top executives are not expected to land in prison, nor are any problem banks in jeopardy of shutting down.
Still, fearing a certain fallout from the new round of scrutiny, banks have bolstered their legal teams. Standard Chartered, for instance, has retained one of the most lauded litigators in the country, Theodore V. Wells Jr., to work on the reopened sanctions case, according to the lawyers briefed on the matter.
The decision to revisit the cases also draws attention to consulting firms that helped shape the original settlements. When determining the extent of wrongdoing at a bank, the government often relies on assessments from consultants that are handpicked and paid by the same bank.
The Bank of Tokyo-Mitsubishi case demonstrated the potential pitfalls of that approach. When Mr. Lawsky made his initial $250 million settlement with the bank last year, the punishment was based partly on an outside consultant's estimate of the illegal dealings. But the New York State regulator has since uncovered emails indicating that the consultant, PricewaterhouseCoopers, watered down the report under pressure from the bank, according to regulatory records.
In August, Mr. Lawsky imposed a $25 million penalty on PricewaterhouseCoopers, which said at the time that the report was "detailed" and "disclosed the relevant facts."
After that settlement, people briefed on the matter said, prosecutors at the Manhattan district attorney's office opened an investigation into the work that PricewaterhouseCoopers did for the Japanese bank, a previously unreported development. Already, the prosecutors have requested the consulting firm's records in the case.
The investigations, the people said, also unearthed emails showing that PricewaterhouseCoopers changed the report not only at the suggestion of the bank, but also at the behest of lawyers working on the bank's behalf. Like many banks caught in the government's cross hairs, the Bank of Tokyo-Mitsubishi turned to Sullivan & Cromwell, an elite law firm as woven into the fabric of Wall Street as the banks it represents. Sullivan & Cromwell also represented Standard Chartered in the bank's 2012 settlement with the Justice Department in Washington and the district attorney's office in Manhattan.
More recently, the government has grown skeptical of the argument that some banks are simply too big to charge, an argument that Sullivan & Cromwell often employs for its clients. That argument was tested in a recent case against BNP Paribas, the giant French bank accused of processing billions of dollars for Sudan and Iran.
At a meeting in Washington this year, a lawyer from Sullivan & Cromwell cautioned prosecutors about the potential fallout from BNP pleading guilty to a crime, according to people briefed on the meeting. To illustrate the concern, the lawyer presented prosecutors with a fake newspaper article reporting that a huge bank had pleaded guilty for the first time in decades. The hypothetical report detailed what regulatory problems could befall the bank if prosecutors did not lower their demands for a fine and take precautions when extracting a plea.
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Weeks later, after lowering the fine to $8.9 billion, the prosecutors forced the bank to plead guilty. Far from reporting a crisis, BNP's chief executive that day noted that the bank "will once again post solid results this quarter."
Not every bank will have to plead guilty in future cases. Prosecutors still see benefits from deferred-prosecution agreements, which can require banks to install independent monitors and more broadly overhaul their practices than in the event of a guilty plea.
Lawmakers and other critics, however, contend that the agreements can lack teeth, begetting a pattern of misbehavior.
Since 2001, at least eight big banks have committed further offenses after receiving an initial deferred-prosecution agreement, according to data assembled by Brandon L. Garrett, a University of Virginia law school professor and author of the book, "Too Big to Jail: How Prosecutors Compromise With Corporations."
UBS has reached three deferred or nonprosecution agreements since 2009. On Tuesday, the Swiss bank said it had reached an agreement with the Justice Department to extend by another year a two-year nonprosecution agreement that was scheduled to expire in December.
The cycle of misbehavior is difficult to break.
Regulators and prosecutors blame a culture that prioritizes profit over compliance. And as banks have grown larger, and more international, illegality can stop in one unit of a bank even as it flourishes in another.
Standard Chartered is at risk of becoming Exhibit A of corporate backsliding. The Justice Department's criminal division in Washington and the district attorney's office in Manhattan, which settled with Standard Chartered in 2012 over its business dealings with Iran, are exploring whether the bank repeatedly violated that deferred-prosecution agreement.