The research of racial scientist Dr. Robert Ritter and his associates served both as instrument and justification for the Nazi regime to isolate and eventually destroy the German Gypsy population. By studying Gypsies, Ritter, who was a psychiatrist, hoped to determine the links between heredity and criminality. With funding from the German Association for Scientific Research and access to police records, Ritter began in 1937 to systematically interview all the Gypsies residing in Germany. To do so, he traveled to Gypsy encampments and, after the deportation and internment of Gypsies began, to the concentration camps. Ritter developed detailed genealogies—family histories to distinguish "pure" Gypsies from those of "mixed blood" and to root out assimilated Gypsies from the general German population. The state police aided Ritter in this by requiring genealogical registration of all Gypsies forcibly moved into special municipal camps after 1935. Believing anyone with Gypsy blood to be a danger to society, Ritter classified a "part-Gypsy" as someone with one or two Gypsy grandparents or two or more part-Gypsy grandparents, that is, someone with as little as one-eighth Gypsy blood.
Ritter's associates included the anthropologist Dr. Adolf Würth and, until 1942, the zoologist and anthropologist Dr. Sophie Ehrhardt. Ritter's closest associate was Eva Justin, a nurse who, received her doctorate in anthropology in 1944 based on her research with Gypsy children raised apart from their families. At the conclusion of her study, these children were deported to Auschwitz, where all but a few were killed.
In a report of his research findings in 1940, Ritter concluded that 90 percent of the Gypsies native to Germany were "of mixed blood." He described such Gypsies as "the products of matings with the German criminal asocial subproletariat." He further characterized Gypsies as a "primitive" people incapable of real social adaptation."
From late 1944 through 1946, Ritter taught criminal biology at the University of Tübingen; in 1947 he joined the Frankfurt Health Office as a children's physician. While there, he employed Eva Justin as a psychologist. His collaborator Dr. Sophie Ehrhardt joined the anthropology faculty at the University of Tübingen in 1942 and continued to use Ritter's data in her postwar research. Dr. Adolph Würth served in the Baden-Württemberg Bureau of Statistics until 1970.
Efforts to bring charges against Ritter and his associates as accessories in the deaths of the German Gypsies were discontinued. The trial of Dr. Robert Ritter ended with his suicide in 1950.