Financial crimes might be too complicated to take to trial.
The mistrial [in the Dewey & LeBoeuf case], after four months in court and 22 days of deliberations, hints at a much deeper problem: Perhaps most financial crime has reached a level of such complexity that it’s beyond the reach of the law.
Since the financial crisis sent the economy into a spiral, leading to millions of lost jobs and foreclosed homes, there have been public cries to see bankers responsible for the frauds underpinning the crisis put in jail. This would have fit with the pattern of how things have gone since the beginning of time: Booms and bubbles led to market collapses and crises, followed by the tightening of regulations and criminal prosecutions. In the case of 2008, however, the crackdown never really came.
Source: Has It Become Impossible to Prosecute White-Collar Crime? – Bloomberg