The "Sterilization Law" explained the importance of weeding out so-called genetic defects from the total German gene pool:
Since the National Revolution public opinion has become increasingly preoccupied with questions of demographic policy and the continuing decline in the birthrate. However, it is not only the decline in population which is a cause for serious concern but equally the increasingly evident genetic composition of our people. Whereas the hereditarily healthy families have for the most part adopted a policy of having only one or two children, countless numbers of inferiors and those suffering from hereditary conditions are reproducing unrestrainedly while their sick and asocial offspring burden the community.
Some scientists and physicians opposed the involuntary aspect of the law while others pointed to possible flaws. But the designation of specific conditions as inherited, and the desire to eliminate such illnesses or handicaps from the population, generally reflected the scientific and medical thinking of the day in Germany and elsewhere.
Nazi Germany was not the first or only country to sterilize people considered "abnormal." Before Hitler, the United States led the world in forced sterilizations. Between 1907 and 1939, more than 30,000 people in twenty-nine states were sterilized, many of them unknowingly or against their will, while they were incarcerated in prisons or institutions for the mentally ill. Nearly half the operations were carried out in California. Advocates of sterilization policies in both Germany and the United States were influenced by eugenics. This sociobiological theory took Charles Darwin's principle of natural selection and applied it to society. Eugenicists believed the human race could be improved by controlled breeding.
Still, no nation carried sterilization as far as Hitler's Germany. The forced sterilizations began in January 1934, and altogether an estimated 300,000 to 400,000 people were sterilized under the law. A diagnosis of "feeblemindedness" provided the grounds in the majority of cases, followed by schizophrenia and epilepsy. The usual method of sterilization was vasectomy and ligation of ovarian tubes of women. Irradiation (x-rays or radium) was used in a small number of cases. Several thousand people died as a result of the operations, women disproportionately because of the greater risks of tubal ligation.
Most of the persons targeted by the law were patients in mental hospitals and other institutions. The majority of those sterilized were between the ages of twenty and forty, about equally divided between men and women. Most were "Aryan" Germans. The "Sterilization Law" did not target so-called racial groups, such as Jews and Gypsies, although Gypsies were sterilized as deviant "asocials," as were some homosexuals. Also, about 500 teenagers of mixed African and German parentage (the offspring of French colonial troops stationed in the Rhineland in the early 1920s) were sterilized because of their race, by secret order, outside the provisions of the law.
Although the "Sterilization Law" sometimes functioned arbitrarily, the semblance of legality underpinning it was important to the Nazi regime. More than 200 Hereditary Health Courts were set up across Germany and, later, annexed territories. Each was made up of two physicians and one district judge. Doctors were required to register with these courts every known case of hereditary illness. Appeals courts were also established, but few decisions were ever reversed. Exemptions were sometimes given artists or other talented persons afflicted with mental illnesses. The "Sterilization Law" was followed by the Marriage Law of 1935, which required for all marriages proof that any offspring from the union would not be afflicted with a disabling hereditary disease.
Only the Roman Catholic Church, for doctrinal reasons, opposed the sterilization program consistently; most German Protestant churches accepted and often cooperated with the policy. Popular films such as Das Erbe ("Inheritance") helped build public support for government policies by stigmatizing the mentally ill and the handicapped and highlighting the costs of care. School mathematics books posed such questions as: "The construction of a lunatic asylum costs 6 million marks. How many houses at 15,000 marks each could have been built for that amount?"