Cohn's antics in relation to his work on the McCarthy's committee would eventually lead to his downfall after he attempted to blackmail the Army in return for preferential treatment for committee consultant and Cohn’s rumored lover, David Schine.
After he was forced to leave McCarthy’s side due to the scandal, Cohn returned to New York to live with his mother and practice law. A few years later New York Judge David Peck, a long-time associate of former CIA Director Alan Dulles, orchestrated Cohn’s hire to the New York law firm Saxe, Bacon and O’Shea. Upon his hire, Cohn brought the firm a slew of Mafia-linked clients, including high-ranking members of the Gambino crime family and the Genovese crime family.
https://www.thoughtco.com/roy-cohn-biography-4151275
https://www.thewrap.com/roy-cohn-cousin-5-things-to-know/