Cavolo's familiarity with Italians and Sicilians and his background on Mayfield Road equipped him to challenge the local Mafia on its home turf. During the Prohibition Era, he was highly successful in organized crime cases.

In 1926, he nabbed a Cleveland gangster for importing a Chicago gunman for a hit against a local man. The following year, he worked on two well publicized murder investigations, those of Samuel Volpe (a sewer contractor found frozen and riddled with bullets in early March) and Louis Nobile.

As a key member of Cleveland's Black Hand Squad, Cavolo helped local newspapers to figure out an underworld feud in the late 1920s and early 1930s.

Gang leader Frank Lonardo was murdered in fall of 1929. His own bodyguard Frank Alessi was suspected. Bootlegger and convicted cop-killer Carmello Licarti was found dead in a Cleveland gutter in early April 1930, a bullet wound in his head and mud stuffed in his mouth. By the end of the month, Alessi - the suspect in the Lonardo murder - was dead. Cavolo immediately arrested Frank Brancato for that killing.

Cavolo was momentarily discredited in February 1931, when it was reported that he helped murderer and thief Ross Valore win parole Cavolo was able to prove that he had no part in the parole. He underscored his position on Valore by securing a statement from the convict's wife that implicated Valore in six murders.

The detective tracked the Hymie Martin-Solly Hart gang to Buffalo, NY, in summer of 1931. The gang was wanted for stealing $45,000 worth of jewelry. Cavolo's bloodhound sense also led to the arrest of Carmine Pigano (alias Benny Nacci) on Cleveland streets in 1938. Pigano was wanted in Dearborn, Mich., in connection with the 1930 kidnapping of a nine-year-old boy.

In 1940, as head of the police automobile bureau, Cavolo unearthed a tire theft ring with headquarters in Cleveland and Buffalo. Stolen tires were transported to a Buffalo clearinghouse. Police estimated that the thieves had earned a million dollars through the racket.