The ongoing trial of Lindsay Clancy in Massachusetts has renewed attention to one of the most challenging intersections between psychiatry and criminal law: how courts evaluate criminal responsibility when a severe mental health condition is alleged. Clancy is charged with killing her three children in January 2023. Her defence contends that she lacked criminal responsibility because of postpartum psychosis (PPP) and a bipolar-spectrum condition, whereas prosecutors maintain that she was criminally responsible. Because the trial remains ongoing, these competing clinical and legal formulations should not be treated as established conclusions. PPP is a severe psychiatric emergency affecting approximately 1–2 per 1000 births, characterised by the acute onset of affective, psychotic and often cognitive or disorganised symptoms.
Clinical, familial, and genetic evidence supports a close relationship between PPP and bipolar-spectrum disorder, leading a recent international expert consensus group to propose its formal recognition as a distinct condition within the bipolar spectrum. Although PPP is associated with elevated risks of suicide and infant harm, maternal filicide remains an uncommon outcome, and the diagnosis should not be equated with violence. Timing is diagnostically important. The recent expert consensus proposes that the defining episode begins within 12 weeks of childbirth, although most episodes begin within the first two weeks postpartum. In retrospective forensic evaluation, the term ‘postpartum’ should not itself establish an aetiological relationship to childbirth; evaluators should reconstruct the actual onset and evolution of the putative episode.