Expulsion of Members of Congress: Legal Authority and Historical Practice [January 11, 2018] [open pdf - 857KB]
"This report discusses the nature of the power of Congress to remove a Member, including the historical background of the Clause, the implications of the limited judicial interpretations of the Clause's meaning, and other potential constitutional limitations in the exercise of the expulsion power. The report then analyzes the potential grounds upon which a Member might be expelled, including an overview of past cases resulting in expulsion and a discussion of the potential exercise of the expulsion power for conduct occurring prior to the Member's election or reelection to Congress."
CRS Report for Congress, R45078
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html