Interest in psychiatrists' professional liability in Italy has increased in recent years because of the number of medical malpractice claims. Professional liability for failure to prevent violent behaviour by psychiatric patients is particularly debated. This study describes three Italian cases in which health professionals - physicians and nurses - were found guilty of manslaughter for murders committed by psychiatric patients. Examination of the cases focuses on claims of malpractice, patients' characteristics, the circumstances of the homicide and the reasons for the court's judgment. In particular, the predictability of violent behaviour and the concept of causal links are examined in detail. The cases provide an opportunity for a study of comparative jurisprudence. The topics discussed are relevant not only to practicing psychiatrists but also to experts assessing medical liability in cases of criminal acts committed by psychiatric patients.