These nurses, caregivers and doctors who became serial killers

This is the story of Katariina Meri-Tuulia Pantila, a 28-year-old Finnish nurse who, in 2007, attempted to inject an eight-month-old infant with insulin during a family celebration. Her arrest uncovered a far more disturbing case. The investigation revealed that she had been working at a home for the disabled where, a week earlier, two residents had died unexpectedly, without a satisfactory medical explanation. In one case, an autopsy revealed a needlestick containing insulin, even though the patient was not receiving insulin therapy.

Sentenced to life imprisonment for murdering a disabled person and causing bodily harm to an infant, the nurse took her own life in prison.

But the investigation didn't stop there. Finnish judicial authorities decided to decipher the nurse's professional background. It turned out that she had previously worked for seven months in a geriatric care unit.

Deaths occurring during this period were re-examined using statistical tools designed to assess the likelihood that she was involved in suspicious deaths occurring in this geriatric unit.

To conduct a rigorous, objective, and transparent assessment, the authorities subjected all 69 nurses who worked in this unit to the same statistical analysis. The objective: to determine whether any tangible evidence specifically identifies this nurse.

At the same time, investigators looked for inconsistencies between death certificates and the patients' clinical course and performed forensic autopsies on several exhumed bodies. One by one, the clues gradually drew the chilling profile of a serial killer in a white coat.

This is what we learn from the article published in February 2025 by researchers from the University of Tampere (Finland) in the journal Forensic Science International.

Between November 2006 and June 2007, this nurse worked in a 32-bed geriatric unit attached to the municipal health center. During these eight months, 29 patients died there. According to medical records and police interviews, the nurse was involved in the care of 11 of these patients, or 38% of the deaths. For each of them, the death certificate attributed death to the illness that led to hospitalization. No autopsy, clinical or ordered by the court, was performed at the time of the events.

Five of the eleven bodies were cremated. Autopsies were performed on the other six bodies between three and eight months after death: five were exhumed several months later, and the sixth was donated to an anatomy department.

The investigators then broadened their scope of analysis by using a method initially developed to measure the relevance of diagnostic tests. Their goal: to assess the degree of involvement of nursing staff members in the 29 deaths that occurred in the geriatric unit.

The data analyzed were considerable: 27,324 shifts, distributed among 30 registered nurses, 27 nursing assistants, and 12 nursing or medical students. Each shift during which a death occurred was classified as "directly involved." If death occurred within eight hours of the end of the shift, the shift was considered "possibly involved." All others were classified as "not involved." The analysis aimed to determine whether there was a significant statistical link between certain caregivers and the occurrence of deaths.

To determine whether the presence of a caregiver at the time of a death was purely coincidental or should, on the contrary, raise suspicion, the researchers evaluated two elements. First, they calculated how many deaths occurred during or immediately after a caregiver's shifts: the higher the figure, the more likely it was to suggest a link. Second, they examined how many times the same person had worked without any deaths occurring. If a caregiver is regularly present at the time of deaths, but rarely there when everything is going normally, this creates a statistical imbalance that could raise alarm bells. Conversely, if deaths are as likely to occur in their absence as in their presence, this tends to rule out direct involvement. Comparisons were made, using specialized software, for each staff member, a total of 69 people.

Here's what stands out: in the geriatric unit, deaths were twice as frequent during night shifts as during other shifts. And this trend isn't solely explained by the longer duration of night shifts, which last ten hours compared to eight during the day.

Of all the caregivers, the nurse convicted of murder worked an abnormally high number of evening and night shifts. She worked 38 evening shifts, while her fellow nurses worked an average of 26. For nursing assistants, the average dropped to 18.

The gap is even more striking at night: the nurse in question worked 19 night shifts, a number significantly higher than that of most of her colleagues, both nurses and nursing assistants, who worked an average of 7 or 8. In other words, she is among the 10% of staff who worked the greatest number of night shifts.

When statisticians examined deaths in the unit, they found that this nurse was particularly present at the time of deaths, or just before. Again, she was among the top 10% of nursing staff who provided the most shifts immediately before or at the time of a patient's death.

Even taking into account that deaths are more frequent at night, the presence of this nurse during these events appears quite unusual. The figures clearly show that the more night shifts she worked, the greater the number of deaths in her presence. Moreover, when the analysis is limited to staff who completed at least five night shifts (in order to neutralize the effect of higher mortality at night), this nurse clearly stands out, with a frequency of deaths much higher than that of other caregivers.

Of the 29 deaths, 11 (38%) occurred during this nurse's shifts. Due to the fragility of elderly hospitalized patients, none of these deaths aroused suspicion among staff, including the doctor in charge.

In each case, the official cause of death corresponded to the illness for which the patient was hospitalized or receiving treatment. None of the deaths were deemed suspicious, even though certain symptoms and circumstances could, or should, have alerted doctors.

It turns out that five cases were considered particularly suspicious due to inconsistencies between the fatal outcome and the death certificates. In all five cases, an unexplained coma preceded death, which is difficult to explain by the pathology listed as the official cause of death. Furthermore, in two cases, nurses had noted profuse sweating, a typical symptom, for example, of hypoglycemia.

These five suspicious deaths were concentrated in the last two months of the seven during which this nurse worked in the ward. "In hindsight, knowing that she had used insulin to kill one disabled person and attempted to kill another, it is plausible that she was responsible for one death from hypoglycemia, as well as other suspicious deaths that occurred in the ward," the authors state.

The statistical approach used by Pekka Karhumen and his colleagues made it possible to reduce the number of suspects and focus the investigation on the healthcare workers whose presence most frequently coincided with the deaths. However, it did not allow a suspect to be formally identified or to provide irrefutable evidence. As the authors point out, the limited number of deaths (29) constitutes a significant limitation for the statistical evaluation. For the record, in 2000, a British general practitioner was convicted of 15 murders and suspected of having killed more than 200 of his patients before being unmasked. We will return to this point.

The authors also emphasize another difficulty: the severity of pathologies and the naturally high mortality in a geriatric population make it particularly difficult to detect suspicious deaths. "According to our observations, the fact that none of these deaths, although clearly suspicious, aroused the attention of the responsible physician could be explained by a certain indifference towards the precise identification of the causes of death in the elderly." They add: "The decrease in the number of autopsies worldwide also contributes to the fact that the cause of death escapes any verification."

In the context of a criminal investigation or trial, statistical analysis is obviously not sufficient to demonstrate guilt. However, it can strengthen a body of evidence or corroborate other evidence. That said, the authors point out that in several criminal cases, the use of statistics has given rise to strong reservations.

This is how nurses Lucia de Berk in the Netherlands and Daniela Poggiali in Italy, both accused of killing several patients, had their convictions overturned after a reexamination of their cases. These emblematic cases illustrate the limitations and potential pitfalls of using statistical methods in a legal context. They also show how statistical data can be open to divergent interpretations. The defense can indeed use them to demonstrate that the prosecution has not proven guilt beyond a reasonable doubt.

The authors of the Finnish study themselves acknowledge this in the conclusion of their article: "Our approach allowed for a comprehensive and objective assessment of all personnel, thus avoiding wrongly targeting an initial suspect, but it did not allow for the identification of a single perpetrator."

One can't help but wonder what artificial intelligence would have concluded from this vast data set, had the Finnish team chosen to use this tool rather than traditional statistical analysis. Would it have detected more subtle modi operandi, uncovered other correlations, narrowed down the circle of suspects, or even affirmed that the nurse was definitely guilty? No one can say, but the question is worth asking.

After this Finnish case, let us look at other cases involving healthcare workers, hospital doctors or general practitioners, found guilty of serial murders.

Among the most high-profile cases of serial killers in the medical field, that of Dr. Harold Shipman occupies a special place. This once highly respected British general practitioner was convicted of the murders of fifteen female patients. But subsequent investigations revealed a much higher death toll: it is estimated that he caused the deaths of 220 to 240 people during his career.

Sentenced to life imprisonment in 2000 for murder and forgery of a will, Shipman practiced in the small town of Hyde, near Manchester, where he enjoyed a solid reputation.

After his arrest in September 1998, analysis of available data revealed an abnormal excess mortality among his elderly patients. In the area where he practiced, the mortality rate for women over 65 was 2.7 deaths per 100 patients. This rate was ten times higher, reaching 26 deaths per 100 patients followed by Dr. Shipman.

The British Department of Health then ordered a comprehensive statistical analysis of the deaths that occurred during Dr. Shipman's career. In the 15 murder cases brought to trial, all the victims were elderly women.

The experts examined 267 medical records in detail, 180 of which included a death certificate signed by Shipman. More than half of these cases (57%) had highly suspicious characteristics: deaths that occurred suddenly at home, often in the presence of the doctor, mainly in the afternoon, and without relatives present.

Compared to patients treated by other general practitioners, Shipman's patients died more often in the afternoon (55% versus 25%), in the presence of the doctor (19% versus 0.8%), or conversely without any witness (40% versus 19%). The presence of a relative at the time of death was also much less frequent (40% versus 80%). In addition, death occurred more quickly: 60% of Shipman's patients died in less than 29 minutes, compared to 23% for other practitioners.

These statistical elements were reinforced by the results of toxicological analyses carried out on nine exhumed bodies. Analysis of skeletal muscles revealed significant concentrations of morphine. The administration of lethal doses of diamorphine, a powerful morphine derivative used in pharmaceuticals, was identified as the cause of death.

Like Harold Shipman, another doctor left behind a long list of victims: Dr. Michael Swango. He, too, took advantage of his position within the healthcare system to kill patients under his care. He is believed to have caused the deaths of approximately 60 people in the United States and Zimbabwe. In his diary, he wrote that "the sweet, heavy smell of indoor murder" reminded him that he was "still alive."

More recently, in 2015, a jury in California convicted Dr. Hsiu Ying “Lisa” Tseng of murder for causing the deaths of three patients to whom she had prescribed addictive and potentially lethal substances for profit, without any real medical indication. Tseng opened her practice in Rowland Heights, a suburb east of Los Angeles, in 2005. Within three years, nine of her patients had died of drug overdoses. Despite these deaths, she continued to dispense large quantities of opioids and anti-anxiety medications, raking in over $5 million in revenue. In October 2015, she was convicted of three murders and sentenced to a mandatory 30-year, up to life, prison sentence. This is the first case in the United States in which a physician has been convicted of murder in connection with overprescribing medications that led to fatal overdoses.

Like Doctors Shipman, Swango and Tseng, some non-physician caregivers abused the trust their position placed in them to commit serial murders.

One of the most infamous cases is that of Charles Cullen, a registered nurse. Over a period of sixteen years (1987–2003), he is suspected of causing the deaths of at least forty patients in nine hospitals and one nursing home across New Jersey and Pennsylvania. He himself admitted to murdering thirteen people by administering a cocktail of drugs, including insulin.

Cullen initially claimed to target only critically ill patients, ostensibly for pain relief. However, a review of medical records revealed that several victims, who received a lethal injection of digoxin, a drug that increases heart rate, were not necessarily terminally ill. One patient was even recovering from a severe asthma attack. He was sentenced to eleven life sentences. The story of his crimes, based on Charles Graeber's book (The Good Nurse: A True Story of Medicine, Madness, and Murder) , was adapted for the screen in the film The Good Nurse (Netflix, 2022).

Another career path, that of Genene Jones, is chilling. The events date back to the 1980s. This Texan pediatric nurse exhibited strange, almost ritualistic behaviors at a very early age when she heard the news of a child's death, as if she anticipated these deaths to come. She sometimes claims, disturbingly, to "guess" which children would die during her shifts.

Her colleagues, quickly struck by the accumulation of unexplained events in her presence, began to keep statistical records: it was not so much the number of cardiac arrests occurring in the department that was worrying, but the fact that they occurred almost systematically when she was on duty. The suspicions were raised up the hospital hierarchy, but no concrete action was taken and the deaths continued.

A turning point came when a doctor detected several recent cases of clotting disorders, which he attributed to abnormal heparin use. When questioned, Jones admitted to using a dosage a thousand times higher than standard doses, prompting the hospital to require that all heparin injections be supervised from now on. When she took a month off work, no cardiac arrests were reported during that time, but upon her return, life-threatening emergencies immediately resumed.

Despite growing concern, management was slow to react. The head of cardiovascular surgery threatened to stop referring patients to the pediatric intensive care unit if nothing was done. An emergency meeting was convened, bringing together American and Canadian experts, but no consensus could be reached regarding criminal liability, partly because, as is often the case in these cases, it was the caregiver himself who wrote the report of the events preceding the cardiac arrest.

Jones was then discreetly removed from the hospital due to new rules reserving intensive care for registered nurses. She immediately retreated to a clinic run by a friend. Shortly after her arrival, a child died suddenly there. Analysis revealed the presence of succinylcholine, a curare used in anesthesia. In addition, a vial containing this substance was found in her environment. It was this material evidence that finally allowed her to be incriminated. She was sentenced to 159 years in prison.

In 2016, Canadian public opinion was shocked when an Ontario nurse, Elizabeth Wettlaufer, admitted to murdering long-term care patients. A 2020 article in Canadian Family Physician magazine summarized the case. Wettlaufer graduated in 1995. A year later, she was caught stealing opioids from the retirement home where she worked. Her license was subsequently suspended for six months by the College of Nurses of Ontario. She was able to return to work, however, with letters of support attesting to her recovery.

Over the years, she worked in several long-term care homes (LTCs), accumulating complaints. But it was only during a psychiatric hospitalization that she finally confessed to killing eight residents with insulin and committing six attempted murders.

Before that, she had already avoided dismissal thanks to the legally mandated support of the Ontario Nurses' Association. A compromise was then reached: no trace of the affair would appear in her file, and the facility was forbidden from alerting future employers. As a result, she was then hired at another retirement home, where she claimed another victim. The commission of inquiry acknowledged that Wettlaufer would not have been unmasked if she had not confessed.

While the Wettlaufer case reveals serious flaws in the healthcare system, the story of Donald Harvey, another serial killer in the medical field, demonstrates the terrifying scale such crimes can reach. Active from 1970 to 1987, he was charged and convicted of 49 murders, 37 in Ohio and 12 in Kentucky. He confessed to 87 of them. Eighty-seven!

He began his career as a nursing assistant. Taking advantage of his privileged access to vulnerable patients, Harvey used a variety of methods: poisoning with cyanide, arsenic, or rat poison, lethal injections, suffocation with a pillow, and sabotage of medical devices (disconnecting the ventilator).

He notably premeditated the murder of an 81-year-old patient. A few days earlier, the octogenarian had hit him on the head with a urinal, before spilling the contents over him, claiming to have mistaken him for a burglar. In retaliation, Harvey chose to use a 20-gauge urinary catheter, usually reserved for women, rather than the thinner 18-gauge catheter suitable for men. He then straightened a wire coat hanger and inserted approximately 60 centimeters of wire into the urinary catheter, perforating the patient's bladder and bowel. The patient immediately went into shock and then slipped into a coma. Harvey then got rid of the wire and discreetly replaced the catheter with a male model, thus attempting to cover up any traces of his actions.

Harvey claimed to want to "relieve suffering," but eventually admitted that he took some pleasure in "playing God." His murder spree ended in 1987 after a medical examiner noticed an odor suggestive of cyanide in his stomach, leading to his arrest. Harvey pleaded guilty to 24 murders and was sentenced to three life sentences (in Ohio) and then to life in Kentucky. He was murdered in prison in 201.

It's impossible to conclude this post without mentioning Kristen Gilbert, nicknamed "The Angel of Death." This American nurse was regularly present during unexplained cardiac arrests, causing concern among her colleagues and several doctors, to the point that some demanded that she no longer be assigned to their patients.

Working since 1989 at the VA hospital in Northampton, Massachusetts, she operated in a morbid atmosphere: the mortality rate in her department was three times higher than in other units. A particularly disturbing detail is the institution's policy that required the presence of a security guard during emergency interventions, an officer who was none other than her lover. This situation suggests that the critical situations she provoked served as a pretext to fuel a relationship based on danger and manipulation.

As suspicions mount, several colleagues take it upon themselves to discreetly monitor stocks of epinephrine, the powerful cardiac stimulant. They quickly discover used syringes in the trash and spot suspicious bottles in the intensive care unit.

While the lure of profit often motivates some criminal caregivers, particularly for insurance or inheritance reasons, the Kristen Gilbert case reveals a more disturbing reality: romantic or sexual fantasy can also be at the heart of the motivations of some killers in white coats.

To find out more: