After the war he studied law at the Humboldt University of Berlin in East Berlin, but in 1948 moved to the University of Wisconsin–Madison and then to the Free University of Berlin in West Berlin.
He served as the 4th president of the Federal Constitutional Court of Germany from 1971 to 1983. Benda briefly served as Minister of the Interior of Germany (1968 to 1969). After school he served in the Kriegsmarine from 1943 to 1945.
1956 he started to work as a lawyer in Berlin.
1957 he was elected to the Bundestag, the West German parliament. In 1965 he was involved in bringing significant changes to West Germany"s statutes of limitations for murder.
Without these changes it would not have been possible to bring charges of murder against erstwhile National Socialists. Since 1967 he was Secretary of State in the German interior ministry and since 1968 Minister of the Interior.
1969 he was appointed as a judge to the Federal Constitutional Court of Germany.
From 1971 to 1983 he was president of the court. From 1984 Benda was professor of law at the University of Freiburg. 1974 Grand Cross of Merit of the Italian Republic.
From 1946 Benda was member of the Christian Democratic Union (Christian Democratic Union). From 1954 to 1957 he was member of the Abgeordnetenhaus von Berlin, the parliament of Berlin.
Married Waltraut Vorbau in 1956.