Dr Robert Ritter.

Robert Ritter's explanation of how the Gypsies came to be of "inferior blood" is a startling example of science driven by ideology. The Gypsies who left India in the 10th century, Ritter argued, were pure Aryans. However, as they migrated westward and intermingled with inferior races -- e.g., in Persia, Armenia, the Slavic countries -- they lost their pure Aryan characteristics. The inferior blood gave them racial characteristics which predispose them to a set of asocial and criminal tendencies. He recommended the segregation of all gypsies and the sterilization of those who were of obviously impure strains. Ritter's research came to the attention of Himmler and, by mid-summer, 1937, he called for a careful evaluation of the research on the Rom.

In September 1939, Reinhard Heydrich organized an official conference of racial policy. The conference was held in Berlin on September 21. While the primary concern of the meeting was to plan the systematic deportation of Jews to Poland, it was also decided relocate 30,000 German Gypsies. In preparation for that deportation, the conference called for the segregation of Gypsies in special camps. While the deportation of Gypsies took a back seat to the deportation of Jews and the desired 30,000 was not immediately achieved, several thousand were deported.

At this point it is important to remember that on September 1, 1939, Hitler ordered the invasion of Poland. Under Heydrich's command, the Einsatzgruppen, or mobile killing units followed the regular Wehrmacht troops into Poland. Their assigned task was to eliminate political criminals, asocials, undesirables, communists -- anyone who posed a security threat to the Reich.

It is not known how many Gypsies were killed by the Einsatzgruppen charged with speedy extermination by shooting. For the sake of efficiency Gypsies were also shot naked, facing their pre-dug graves. According to the Nazi experts, shooting Jews was easier, they stood still, `while the Gypies cry out, howl, and move constantly, even when they are already standing on the shooting ground. Some of them even jumped into the ditch before the volley and pretended to be dead.'(Raul Hilberg, The Destruction of the European Jews. Chicago: Quadrangle Books, 1961:439
According to Helen Fein, Accounting for Genocide, 1979:

In 1939, resettlement of Gypsies was put under Eichmann's jurisdiction along with that of the Jews. Gypsies were forbidden to move freely and were concentrated in encampments with Germany in 1939, later (1941) transformed into fenced ghettos, from which they would be seized for transport by the criminal police (aided by dogs) and dispatched to Auschwitz in February 1943. During May 1940, about 3,100 were sent to Jewish ghettos in the Government-General: others may have been added to Jewish transports from Berlin, Vienna, and Prague to Nisko, Poland (the sight of an aborted reservation to which Jews were deported). These measures were taken against Gypsies who had no claim to exemption because of having an Aryan spouse or having been regularly employed for five years.

On December 16 1942, Himmler ordered the deportation of all Gypsies to Auschwitz. This is the official beginning of a "Final Solution" to the Gypsy Nuisance. At Auschwitz, the Gypsies were held in Camp B IIe. This is the designation for the larger Camp at Birkenau. Many were used in Joseph Mengele's medical experimentation, others were used in the German Air Force tests on reactions to extreme freezing temperatures, thousands were sent to the gas chambers. Similar fates for Gypsies are reported at Treblinka, Chelmo and other extermination centers.

Link here.