Slovik was born in Detroit, Michigan, in 1920 to a Polish-American family, the son of Anna and Josef Slowikowski.[6][7] As a minor, he was a troublemaker and had contact with the police frequently. Slovik was first arrested at 12 years old when he and some friends broke into a foundry to steal brass.[8] Between 1932 and 1937, he was arrested several times for offenses which included petty theft, breaking and entering, and disturbing the peace. In October 1937 he was sent to prison, but was paroled in September 1938.