His remarks came 18 months after his infamous "too big to jail" comment, which suggested the collateral damage of charging banks might be too great for the system to bear.
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Zamansky, a former prosecutor with the Federal Trade Commission, said investors are still outraged and want answers.
"They ask me all the time, 'why hasn't anybody gone to jail?'" he said.
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It was a different story in the early 2000s, he added, when there were convictions against top executives at Enron, WorldCom, Adelphia and Tyco.
"They had the will. I think it's more the will and direction from the top to go after these people," Zamansky said. "I certainly don't see why they can't do it now with whistleblowers, with the investigative techniques that they have."
However, investigations stretching back to the financial crisis may have some issues since six years have passed.
"Documents disappear, people's memories fade. They should have been in there quickly," he said.
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However, he thinks either way the public needs answers.
"If you've got something step up and make the case. If not, then tell us you couldn't find the smoking gun … but we need to know what happened and whether there was criminal wrongdoing," Zamansky said.
—By CNBC's Michelle Fox. CNBC's Kate Kelly contributed to this report.