In the late nineteenth century, a number of intellectual currents converged to produce a crisis in how Britons, in England and in the wider British empire, understood criminality and its implications for common law doctrines premised on free will and the ideal of the autonomous, rational individual. These anxieties crystallized in what we might call ‘responsibility cases’: high-profile criminal cases, usually involving homicide, in which judges, lawyers, medical men and members of the public tested the boundary between biology and agency. I focus on a sub-group of defendants who only occasionally figured in such cases: women. Their cases were less likely to elicit the kind of jurisprudential and philosophical agonizing that regularly marked those involving male defendants, despite the fact that women were believed to be particularly vulnerable to insanity. Using criminal cases from a variety of imperial jurisdictions, this talk reintegrates violent women into the history of criminal responsibility and complicates our understandings of criminal law and personhood in the British world.