Forensic hospital records of 39 severely mentally ill mothers adjudicated Not Guilty by Reason of Insanity for filicide (child murder by parents) were analyzed to describe characteristics preceding this tragedy and to suggest prevention strategies. Almost three-quarters of the mothers (72%) had previous mental health treatment. Over two thirds (69%) of the mothers were experiencing auditory hallucinations, most frequently command hallucinations, and half (49%) were depressed at the time of the offense. Over one third (38%) of the filicides occurred during pregnancy or the postpartum period, and many had a history of postpartum psychosis. Almost three-quarters (72%) of the mothers had experienced considerable developmental stressors, such as death of their own mother or incest. Maternal motives for filicide were predominantly "altruistic" (meaning murder out of love) or "acutely psychotic" (occurring in the throes of psychosis, without rational motive). Psychiatrists should perform careful risk assessments for filicide in mothers with mental illnesses.