He received his doctorate in 1873 in Würzburg, titled : "About intestinal perforation and typhoid abdominalis". He worked in various Parisian hospitals; later he took an interest in psychiatry. In 1912 he became the director of the psychiatric hospital at Colditz Castle. Näcke, along with Hans Gross, a professor of criminology, founded the archive of criminal anthropology and criminology in Dresden in 1898. In 1884 Näcke wrote the first monograph on women's crime in Germany. He suggested a "sensible emancipation of women", which was groundbreaking for the time, but did not mean equal rights. Näcke is considered a strong opponent of Positive criminology, that was founded by Cesare Lombroso. Näcke described Lombroso's work as marked by "arbitrariness, exaggerations, jumping to conclusions" According to Näcke, criminals are the product of external influences, and not only biological influences as thought by Lombroso. This does not mean that Näcke disapproved of a biological basis for crime altogether. His argument is that every human being is a "latent criminal". Näcke was one of the first advocates of the sterilization of "degenerate criminals" and "degenerates" in general. He saw it as a public duty to make "degenerates" infertile. By 1900, he published a work entitled The castration of certain classes of degenerates as an effective way of social protection Näcke wrote on the subject of a Jewish character, which was described only in vague and general features, and considered that character as a reason for crimes committed by Jews. Näcke stated his position in 1899: "the State has the holy duty to intervene... and to prevent through legislation the increase of the degenerated elements. Such an intervention would aim at the removal of a big cancer in our national body". He asserted that only castration could guarantee that this task was fulfilled both effectively and in the "easiest, cheapest way". In 1912, Näcke wrote against the then common diagnosis of "moral insanity". He developed the idea that homosexuality should not be regarded as a mental illness, but as an innate natural property. He described male menstruation as clear evidence of a continuum between male and female sexuality.
