Final answer:
Al Capone was convicted based on evidence from an accountant's ledger proving he had not paid taxes on his substantial income. Despite his many criminal activities, it was the tax evasion charges that led to his conviction and imprisonment in 1931.
Step-by-step explanation:
The smoking gun to convict Al Capone was an accountant's cash receipts ledger. Capone was a notorious gangster in Chicago during the Prohibition Era, with a criminal empire that included bootlegging, gambling, and other illegal activities. Although he was involved in various crimes, it was ultimately tax evasion charges that led to his conviction. The authorities were able to prove that Capone had substantial income but had not paid taxes on it. Using the ledgers that tracked his income, they were able to convict him in 1931, sending him to prison, including a stint in the infamous Alcatraz.
Tax Evasion and Organized Crime
During Prohibition, organized crime figures like Capone thrived. Capone's operations netted millions annually, but due to the nature of the criminal activities, the FBI couldn't directly link Capone to many of his purported crimes. Instead, they successfully pursued him for tax evasion by focusing on the front businesses that laundered his profits but failed to report the income.