Euthanasia perpetrators were often not tried after the war for a number of reasons. The medical community closed rank and were very very reticent about the crimes which Nazi doctors committed during World War II. Also, Euthanasia crimes in particular failed to resonate with German jurists and later with lay juries. Euthanasia crimes were tried before German jurists, not before Allied occupation authorities interestingly enough, and very often, Euthanasia victims did not inspire the same sort of pity and respect as political persecutees, Jews, concentration camp victims. They failed to draw the sympathy of German and in some cases Allied courts. The idea that these persons had in fact died violent deaths was much more difficult to understand. It’s easy to understand a death on the killing fields of the Soviet Union, or if the persons had died in a concentration camp setting, but these persons—the Nazi medical community, now fully reintegrated into often the West German and in some instances East German medical community, now suggested that they had merely put these persons "to sleep." Euthanasia was in fact a euphemism which Nazis had used during the war to mask a program of mass murder. And after the war, the same word was invoked to suggest that they had put mental patients, severely mentally and physically disabled persons, to sleep.
Museum historian and subject matter expert [2002 interview]