Frank Costello was convicted of contempt of Congress because he walked out of one of the Kefauver hearings before they officially dismissed him. But a gangster could be convicted of contempt of court only if a judge offered him "immunity to testify" and he refused to answer after that. The guys who pleaded the Fifth dozens of times (even hundreds of times), like Tony Accardo and Sam Giancana, weren't jailed but were exposed as guys who had something to hide.