The application of financial investigative techniques to sophisticated forms of CRIME began decades ago in campaigns to bring underworld bosses to justice. They were charged not with the underlying offenses of bootlegging or extortion, but for reaping financial windfalls from activities that either were not federal offenses at the time or that prosecutors just could not prove. Beginning with the federal tax case against Al Capone in 1931, Treasury investigators had to find ways around both the lack of federal laws proscribing racketeering activity and the difficulties in catching underworld bosses for their offenses. The approach was creative but simple: Internal Revenue agents gathered evidence to prove that the racketeers spent more income than they reported on their tax returns. The differential between what was reported and what the government alleged they earned would establish that their target received...