John Marshall Harlan II,
United States v. Johnson (383 U.S. 169…
“ There is little doubt that the instigation of criminal charges against critical or disfavored legislators by the executive in a judicial forum was the chief fear prompting the long struggle for parliamentary privilege in England and, in the context of the American system of separation of powers, is the predominate thrust of the Speech or Debate Clause. In scrutinizing this criminal prosecution, then, we look particularly to the prophylactic purposes of the clause. ”
