 In May 1930, Irey sent Frank J. Wilson, then 42, to lead the investigation into linking Capone to taxable income through his dealings with O'Hare.From the time Wilson and his agents were put on the case, they examined over 2 million documents and evidence acquired in a number of raids on Capone's establishments over a six-year period.Their strategy was to show that Capone was spending a lot of money which would indicate to a jury that the money had to be coming from somewhere even though he did not have a formal job.