The Toronto hospital baby deaths, believed to be homicides, occurred in the Cardiac ward of the Hospital for Sick Children between July 1980 and March 1981. They ended when the police were called in and the digitalis-type medication used for the killings (digoxin) began to be kept under lock and key. Three nurses were at the centre of the investigation, and an apparent attempt to poison nurses' food. One of the nurses, Susan Nelles, was charged with four murders, but the prosecution was dismissed a year later on the grounds that she could not have been responsible for a death not included in the indictment, which the judge deemed a murder.