Update: In a Barrie court in June, 2017, Ontario nurse Joanne Flynn was acquitted of charges of manslaughter and criminal negligence causing death related to a patient. This story has been updated.
Update: Elizabeth Wettlaufer, a former nurse who worked in Woodstock, Ont., pleaded guilty in June, 2017, to eight counts of first-degree murders.
They are sometimes called "angels of death," health-care professionals accused of serial murders in hospitals or care homes, most often against weak or vulnerable patients. The cases are rare, but when they emerge they make headlines around the globe.
In June of 2016, investigators in Germany reported that Niels H., a nurse who had been sentenced to life in prison for killing two patients with intentional overdoses of heart medication, was a suspect in 33 other patient deaths. That same month, a Danish court sentenced nurse Christina Hansen to life in prison for the murders of three patients and the attempted murder of a fourth, using deliberate overdoses of sedatives and morphine.
On Oct. 25, 2016, Canadian nurse Elizabeth Wettlaufer, 49, was arrested and charged with eight counts of first-degree murder in the deaths of elderly patients at long-term care homes in Ontario.
It is believed to be only the second case where a nurse in Canada has been accused of multiple murders of patients, and is among the largest alleged serial killings in Canadian history.
Ms. Wettlaufer is accused of killing the patients by administering drugs.
In the early 1980s, Canada was rocked by investigations into the deaths of babies at Toronto's Hospital for Sick Children, and allegations that 36 babies may have been victims of homicides. A young nurse, Susan Nelles, was charged with murder in the deaths of four infants, but the charges against her were stayed after a preliminary hearing, and she later received financial compensation.
A royal commission that looked into the deaths ultimately concluded eight babies were murdered at the hospital and 15 others may have been, but no suspect was ever identified. Theories later emerged that the deaths may not have been homicides at all.
A small number of single homicide charges against nurses in Canada have also ended with charges being dropped or stayed. There have also been charges against nurses and doctors in individual cases of assisted suicide or mercy killing.
In one such case, Toronto nurse Scott Mataya was charged with first-degree murder in the death of terminally ill 77-year-old Joseph Sauder in 1992, but later pleaded guilty to a lesser charge of administering a noxious substance.
In April, 2015, Ontario nurse Joanna Flynn was charged with manslaughter for allegedly taking 39-year-old patient Deanna Leblanc off life support without authorization, after Ms. Leblanc went in for pain caused by a knee surgery. That case is still before the courts. UPDATE: On June 8, 2017, a jury in Barrie acquitted Ms. Flynn of all charges.
A 2006 research paper entitled Serial Murder by Healthcare Professionals called multiple homicides in a medical environment "a poorly understood but increasingly identified phenomenon."
The study looked at 90 criminal prosecutions of health-care professionals since 1970 that fit the serial murder definition, and excluded assisted suicide cases, individual murders and "the occasional physician or nurse" charged after administering lethal narcotics to the terminally ill. The study noted that in some cases, euthanasia was used as a defence in serial murder.
The study found that nurses were the accused killers in 86 per cent of the health-care serial murder cases. Doctors and other hospital staff made up the remaining 14 per cent of accused.
The study found motivations for the murders included the excitement of trying to revive a patient, or a kind of "professional version of Munchausen Syndrome by Proxy." In the recent case in Germany, the nurse, Mr. H., admitted to inducing cardiac arrests in about 90 patients, because he enjoyed the feeling of being able to resuscitate them.
Other motives included getting "sadistic satisfaction" from killing certain patients, or, in a small number of cases, financial profit.
Very few of the accused health-care serial killers had a previous criminal record, but many had histories of "falsifying credentials or other aspects off their background," the study found.
By 2006, New Jersey nurse Charles Cullen had pleaded guilty to killing 29 patients while working in hospitals and care homes in New Jersey and Pennsylvania. Mr. Cullen estimated he may actually have killed 40 patients over a 16-year period.
He said he hoped his crimes may eventually be seen as mercy killings, though not all of his victims were terminally ill.
In July, an appeal court in England upheld the convictions of a 49-year-old nurse found guilty of killing two patients, attempting to seriously injure another and trying to poison 20 more with insulin. In that case, nurse Victorino Chua described himself as "an angel turned into an evil person."