 They formed the nucleus that became the Intelligence Unit.In that role, Irey formed one of the most successful investigative teams in the history of American law enforcement with agent Frank J. Wilson leading the hundred-man unit of "T-men" in a three-year investigation against Capone's criminal organization the "Chicago Outfit".Despite attempted jury tampering and death threats against Wilson, Irey's investigation succeeded in the conviction of Capone for tax evasion in 1931.