Fred Ries was the cashier at several Capone-controlled gambling operations, including the "Subway", at 4738 W. 22nd St., in Cicero, located where the building pictured above now stands. In large part because Ries was entomophobic (afraid of insects), Jake Guzik, Frank Nitti, and Al Capone ended up in federal prison.
Ries' job as cashier involved collecting the house's winnings each night, converting them into cashier's checks, and then passing cuts of these checks to the Capone Outfit's leadership, including "Scarface" himself. This laundering scheme kept any evidence of income (and thus, tax liability) safely separated from Capone and company. The feds knew Al had plenty of money -- they had seen him lose $20,000 in a night of gambling, plus his substantial real estate holdings -- but they had no way to prove he had earned it as income. Until, that is, they found out that one of Capone's cashiers was deathly afraid of cockroaches.
At the time of his arrest as a material witness, federal agents found Ries hiding out in St. Louis. They threw him into a specially-made cell in Danville, Illinois, which had previously been prepared with roaches, spiders, rats, and bedbugs. After five days in the cell, Ries was ready to talk. He would have done anything to escape that cell.
Based on his grand jury testimony, Guzik, Nitti, and Al Capone were indicated for tax fraud. Of course, during the time between the indictment and the trial, Fred Ries became the #1 mark for Capone's henchmen, which is why the feds sent him on an all-expenses-paid vacation to South America for a month. At trial, Ries' testimony was the coup de grace, the government's final and most convincing witness, tying Al Capone directly to substantial sums of income on which he had never paid taxes.
Capone went to prison for eight years, effectively ending his racketeering career. Ries went into hiding, and apparently was never heard from again.
Fred Ries' operation, the Subway, sat on property which is now the location of a Dunkin' Donuts store (currently being renovated).