His most famous scientific works were a book on forensic toxicology that became a reference work in this field in the 19th century, and a book on the forensic examinations related to ”assault on decency”, a legal term covering indecent exposure, rape and homosexuality. He also wrote a pioneering study on maltreatment against children and he published on the terrible working conditions of young boys and girls in mines and factories. A study of copper workers (both child and adult) led to a radical improvement in their working conditions. Though Tardieu's textbook on the legal medicine of poisoning was the work that did most to establish him as an authority in his time, for the posterity he is most famous for his forensic study of sexual crimes:
Etude Médico-Légale sur les Attentats aux Mœurs. ("Forensic Study of Assaults against Decency"). The study consists of three parts: the first deals with indecent exposures, the second with rape and the third with "pederasty" (sexual relations between an older and a younger man). Written before the term
homosexuality was coined, Tardieu sought to identify external signs of committed ”pederasty” which might help the forensic expert present convincing evidence that a crime had been committed to the court of law. In so doing, Tardieu discussed the causes of homosexuality, without making them the main purpose of his study. He presumed some of the "pederasts" had an inborn inclination, but nevertheless considered the sexual practice in question to be a condemnable vice. Tardieu believed "pederasts" were either exclusively active or passive during anal sex, and that passive pederasts could be detected via their anus. He described males who received anal sex as exhibiting: "excessive development of the buttocks, funnel shaped deformation of the anus, relaxation of the
sphincter, the effacement of the folds, the crests, and the wattles at the circumference of the anus; extreme dilation of the anal orifice; and ulcerations, hemorrhoids, fistules". The findings in this study were later republished in the book
Étude sur les Blessures, which was published in 1879, the year of Tardieu's death. In this, his last book, Tardieu claimed to have been the first physician to publish on this subject. Nonetheless, Tardieu's research on the subject was largely either sharply criticized or ignored by legal authorities and other clinicians. ==Works==