Elizabeth Wettlaufer, the ex-nurse who confessed this week to murdering eight elderly patients in her care, is now near the top of the list of Canada's serial killers — and it's her profession that gives her even more notoriety.

Other Canadian killers have killed more victims: Robert Pickton, for example, confessed to killing 49 women, and Clifford Olson was convicted of 11 murders, largely children.

But after Wettlaufer pleaded guilty Thursday to eight counts of first-degree murder, four counts of attempted murder and two counts of aggravated assault, she became the first convicted serial killer in the history of Canada's health-care system.

Wettlaufer — who administered lethal doses of insulin to victims at two Ontario nursing homes over the course of seven years — is now also among a roster of nurses from around the world who carried out their crimes at work.

Health-care workers who kill are "statistically rare," says Michael Arntfield, an assistant professor at Western University. But when they do, they tend to kill a lot of people before they're stopped.

"It is not entirely surprising that in Canada, our first known health-care serial killer is so prolific," he said, adding that in a field dealing with life and death, these kinds of killers can often go undetected.

Wettlaufer Niagara Falls

Wettlaufer often worked as the nurse in charge on the night shift at long-term care homes in the southern Ontario cities of Woodstock, Paris and London. (Facebook)

In the United States, the most prolific health-care killer is Charles Cullen, a critical care nurse who admitted to killing 40 patients in New Jersey and Pennsylvania during his 16-year career. Case experts suspect it's possible that he could have caused more than 300 deaths.

And Italian nurse Daniela Poggiali is currently in jail, awaiting trial in connection to the deaths of at least 38 patients. Police in that country believe she could be responsible for the deaths of as many as 96 patients; she is accused of poisoning them with potassium chloride and taking selfies with some of the bodies.

In Germany, a former nurse known only as Niels H confessed to killing more than 30 patients, though he was only convicted in two deaths. His trial heard he intentionally brought about cardiac crises in about 90 patients because he liked the feeling of being able to resuscitate them.

'Daily access to victims'

"Health-care serial killers frequently have the highest body count of all serial killers because they have daily access to victims," says Arntfield, who recently wrote a book on serial killers called Murder in Plain English.

Beatrice Yorker, of California State University, has also studied serial killers in the health-care field. She's examined dozens of cases where nurses were prosecuted and says Wettlaufer fits the pattern of many health-care killers.

"She fits the long-term care nursing home profile, which is power, control and an extra-heavy workload — feeling a little sadistic toward the patients," said Yorker.

Elizabeth Wettlaufer describes how she killed a patient0:34

In a taped confession to police that was played in court, Wettlaufer offered various explanations for her actions. At one point, she said she believed that either God or the devil wanted her to kill these people. At other points, she said she was visited by "surges" that she could not control.

Wettlaufer also told police she picked some of her victims because they "were mean," difficult to look after and that she had a heavy workload.

Killers like Wettlaufer are looking to exert power they don't have in their own lives, Arntfield said, and "select patients that essentially just annoy them."

Killers hard to detect 

Some are believed to be motivated by what's called the "angel of death syndrome" or the "Mother Theresa syndrome," where the killers claim they were doing patients a favour and showing mercy by ending their lives.  

Others may crave attention, and will carry out the lethal act, only to then attempt to save the patient so they can get credit for it.

PATIENT DEATHS

Charles Cullen is a former critical care nurse who admitted to killing 40 patients in New Jersey and Pennsylvania during his 16-year career. (Mike Derer/Associated Press)

Both Arntfield and Yorker say nursing homes are ideal environments for serial killers: They have constant access to potential victims, legal access to drugs, there are often no witnesses and the deaths may not be considered suspicious, given the patients are ill and elderly, meaning autopsies are unlikely.

If there are suspicions, they are often expressed too late — after bodies have decomposed, or been cremated or embalmed, when chemical traces can't be detected.

'Canary in a coal mine'

"What we see in cases like Wettlaufer's is that it reveals to us just … what a blind spot in the system health care could be for a motivated offender who wants to exploit that access to vulnerable people," said Arntfield.

Serial killers in health-care settings can be hard to catch and hard to prosecute, but Yorker said some measures have been taken in the U.S. in recent years to prevent what Cullen, Wettlaufer and others were able to do.

Administering medications is now frequently computerized, and hospitals are better at tracking what nurses are giving patients through a rigorous identification system.

"There are a lot of safeguards in place to deter people," she says. "It's not nearly as easy as it used to be to get away with this."

But, she says, it still happens — and misuse of medication isn't always the method. In a recent U.S. case, a nurse was convicted of killing five patients after putting bleach in their dialysis tubes. 

Meanwhile, the Wettlaufer case has prompted calls for a public inquiry to examine what went wrong and how to prevent it from happening again. It's an idea that Arntfield supports.

"This case, to me, is the canary in the coal mine that warns of other potential dangers in the system," he says. "And it needs to be addressed."