“We punish people for intentional misconduct, we don’t punish them for stupidity or innocent mistakes,” he said. “If you’re a prosecutor, you want evidence that shows real dishonesty. You want something that shows that these people were doing something wrong, and they knew it.”

That nearly all of the banking industry acted the same, possibly reckless, way could actually help any executive who lands in court, lawyers said. The herdlike behavior suggested that bankers were competing for business using widely shared assumptions, rather than trying to get away with a crime. It would be hard to prove that anyone broke the rules, these lawyers said, since regulations in the riskiest parts of the mortgage industry were so lax.

One defense lawyer said he expected to argue that either his clients did not understand the financial instruments they were marketing, or were not warned of the dangers by underlings.

“We’ll all sing the stupidity song,” said the lawyer, who said he feared that speaking publicly by name would deter potential clients. “We’ll all sing the ‘These guys never told me’ song.“

But for government lawyers, the environment for corporate fraud cases could scarcely be more inviting. It is not just that the public’s zeal for Wall Street pelts is high. The resources are there, too, because some of the money once used to fight terrorism is being shifted to fighting financial fraud. And in recent years the use of wire fraud statutes has expanded, allowing prosecutors to turn virtually anything said or sent by e-mail in private into a federal crime, if it contradicts what investors were told in public disclosures.

Wire fraud charges were among those against two former Bear Stearns managers who were arrested in June, accused of praising their hedge fund to clients as they worried about it to colleagues. Federal sentencing guidelines also link the length of a prison term to the size of the financial loss to the public. Given that so many billions have vaporized recently, convictions could easily lead to life sentences, defense lawyers said, and the mere threat of such sentences gives prosecutors enormous leverage in settlement talks.

“There are executives now getting sentences longer than murderers and rapists,” said Mr. Petrocelli, the lawyer, referring to white-collar prosecutions in recent years, including that of Mr. Skilling of Enron, who is now serving a 24-year sentence for securities fraud and other crimes.