Through an analysis of records from Broadmoor Criminal Lunatic Asylum, this PhD thesis sheds new light on current understandings of the asylum, masculinity and the relationship between medicine and the law in late-Victorian England and Wales. The material consulted includes a database containing the details of 2246 patients which was compiled from the Admissions Registers as part of this thesis, and the case files of 425 male patients. Newspaper reports, trial proceedings, Home Office records, and medical and legal publications are also consulted, as are publications that sought to define ideal behaviour for men. The sources are woven together to formulate accounts of the crimes committed, the subsequent trials, and defendants’ experiences in Broadmoor. Through an examination of new evidence, this thesis surveys the history of the asylum, its staff, treatment and patients. An examination of paternal child-murderers questions the assumption that it was only women who were thought to be going against nature if they killed their child. An analysis of discourses on jealousy highlights that whilst crimes of passion existed in theory and were common narratives in popular culture, jealous wife and sweetheart murderers were subjects of legal and medical contention. Additionally, the thesis adds to current histories on medico-legal conflict in the late-nineteenth century and highlights the haphazard application of the McNaughton Rules through the use of new examples. Finally, an examination of Broadmoor’s insane convicts, as well as the publications and Addresses of Broadmoor’s Superintendents, sheds new light on the question of the criminal, not only in theory but also regarding their treatment in a criminal lunatic asylum from the point of view of the press, Government, and Broadmoor’s staff and patients.