Erwin Villain (1898-1934) was a medical officer in the Nazi Sturmabteilung (SA-Standartenarzt, with the equivalent rank of colonel). He is believed to have been involved in the Reichstag fire, and his being killed in the Night of the Long Knives may have been another case of purging people with sensitive knowledge.
Villain, chief of the Greater Berlin Physicians Association, was active in the Nazi management of the medical profession, including purging Jews from it, and giving preferential admissions to the health insurance approved panel of doctors. He had been a protege of Reich Physician Leader Gerhard Wagner, a political rival of Reich Health Leader Leonardo Conti; Conti had moved from the SA into the SS. Wagner had been accused of protecting Chief SA Physician Ketterer, a friend of Villain, of accusations of homosexuality. Villain challenged Wagner to a duel, which was forbidden by Hermann Goering, then Wagner's supervisor in the Prussian government. On 4 March, Villain physically attacked Conti and was arrested. He was convicted of assault and sentenced to eight months, cut short by his killing in the purge. Before that, an SA court convened by Ernst Roehm convicted Conti of contempt. 
- Paul R. Maracin (2007), The Night of the Long Knives: Forty-Eight Hours That Changed the History of the World, Globe Pequot, pp. 104 & 137
- Stephan Leibfried and Florian Tennstedt (1986), Health-Insurance Policy and Berufsverbote in the Nazi Takeover, in Donald W. Light ..., Political values and health care: The German experience, MIT Press, p. 167
- Geoffrey Cocks (1997), Psychotherapy in the Third Reich: the Göring Institute, Transaction Publishers, pp. 206-208