Criminal poisoning: medical murderers.

It is impossible to determine the true incidence of homicides that occur within health care facilities. Over the years there have been numerous documented examples of health care providers preying on helpless patients. For several reasons, the health care system has been inadequate in its response. This article reviews some of those cases, the hospitals' responses, and the outcome of investigations,to reveal the common factors that can identify the warning signs of these tragic events.