After the war she was vice president of the Supreme Court of East Germany from 1949 to 1953, a member of the Volkskammer (the East German parliament) from 1949 to 1967, justice minister from 1953 to 1967, and a member of the Central Committee of the SED from 1954 to 1989.
Benjamin was notorious for her judging of "show trials" (for political effect) and ministerial activities. Because she sentenced many people to death, she was nicknamed "Bloody Hilde", "The Red Guillotine", and "Red Freisler".
Later in life she gave lectures about the history of the judiciary in Potsdam.