Frank J. Wilson

Frank J. Wilson (May 19, 1886 – June 22, 1970) was the Chief of the United States Secret Service and a former agent of the Treasury Department's Bureau of Internal Revenue, later known as the Internal Revenue Service, most notably in the 1931 prosecution of Chicago mobster Al Capone and federal representative in the Lindbergh kidnapping case.

Upon joining the United States Treasury Department's Intelligence Unit in 1920, the former accountant Wilson would earn a reputation throughout Prohibition as a thorough, if not obsessive, investigator of tax returns and income.

In 1928, Wilson was assigned by the chief of the Enforcement Branch of the Bureau of Internal Revenue, Elmer L. Irey, to investigate mobster Al Capone in a later federal prosecution for tax evasion. Although earlier investigations regarding racketeering charges had been successfully defended by Capone, Irey believed Capone could be prosecuted under a 1927 ruling by the Supreme Court which declared that any income from criminal activities must be subjected to income taxes.

However, as Capone did not file tax returns, own property, endorse checks, maintain bank accounts or give receipts, his income could not be accounted for. As calculating Capone's net worth and expenditures were crucial to federal prosecutors, Wilson arranged to have Capone's organization, known as the "Chicago Outfit," to be infiltrated by federal agents to gather information on Capone's dealings in bootlegging, illegal gambling, and other vices.

Wilson himself moved into Chicago's Sheridan Plaza Hotel with his wife under the guise of a tourist. Wilson's wife was uninformed of the details of his assignment; instead she had been told that Wilson was investigating the finances of one "Curly Brown." Wilson would spend the next three years gathering information on Capone's financial dealings including tracking down mob accountants and bookkeepers.

...
Wikipedia