Why serial killers like Lucy Letby often work in healthcare.

British nurse Lucy Letby was last week sentenced to life in prison for murdering seven infants in her care, and attempting to murder a further six.

As a forensic criminologist, many people have asked me why a medical professional would murder their patients.

While they’re very rare, serial killer healthcare workers often share common traits, and they target a specific, and very vulnerable, victim pool.

While limited research has been conducted on serial killer medicos, there are some trends among serial killers that can help us understand the role of the profession in the act of serial murder.

‘Custodial’ killers.

A serial killer is usually defined as someone who kills at least three people in a series, but not in a single event – there needs to be a cooling-off period between the killings. Although the public is generally fascinated by these predators, serial killings are a rare event, comprising fewer than 1% of all murders in any given year in the United States.

Serial killers come from many walks of life, and not all are dysfunctional loners – many are married or in a stable relationship.

A 2014 research paper found serial killers can be understood via several subtypes, including: those who kill for sexually sadistic pleasure; professional killers who are motivated by money and the power they derive from the kill; and, as relevant to Letby, “custodial killers”.

Custodial killers are often healthcare workers who murder helpless or dependent people in their care.


The paper’s author writes of custodial killers:

The most common examples include “angel of death” cases involving nurses in hospitals or nursing homes who surreptitiously murder ill or elderly patients, usually by asphyxiation or medication overdose. This group is likely to contain the highest number of female serial killers.

It’s likely the method of murder is linked to their profession. Healthcare workers have access to medications not available to others, as well as the knowledge to hide their crimes more effectively.

One research group studied 64 female serial killers in the US between 1821 and 2008, and found nearly 40% of them worked in healthcare.

But the question remains, why do they kill? If we look at women specifically, the 2014 research paper suggests that, unlike men who murder as a result of predatory lust and/or compulsive rage, women serial killers are typically driven by histrionic attention-seeking or financial gain.

Letby and healthcare killers.

Another research paper specifically studied the characteristics of 16 convicted healthcare serial killers, which the authors defined as “nurses who have been convicted of at least two murders, which they have carried out within a hospital setting”.

While a small sample size, they found 56% were female, and the average age of those being charged was 36 years.

About 44% killed between five and nine victims before being caught, and 75% killed in only one location. Insulin was the most common method of murder, followed by muscle relaxant.

Letby fits several of these characteristics. She’s a woman, 33 years old, and murdered seven infants. She killed, as far as we currently know, in only one location, and she used insulin to murder some of her victims.


A 2007 book, Inside the Minds of Healthcare Serial Killers: Why They Kill, provides a checklist of 22 “red flags” for this group of killers, including:

  • secretive/difficult personal relationships

  • history of depression or mental instability

  • higher incidents of death when they are on shift

  • making colleagues anxious or suspicious

  • craving attention.

Letby certainly made her colleagues suspicious, and they reported her in the years preceding her arrest. There were more child deaths on her shifts than on those of any other staff member, which is how she was caught.

One criminal psychologist suggested part of the rationale behind the killings may have been to gain the attention of a male colleague, whom prosecutors claimed she had a “crush” on. This would fit with research suggesting attention-seeking is a motive for female serial killers more generally.

Other infamous healthcare killers.

Harold Shipman was an English general practitioner who is considered one of the most prolific serial killers in modern history.

He was convicted of murdering 15 of his patients in 2000, but is suspected in the deaths of up to 250 people.

Most of his victims were older women in good health. He killed many by injecting them with lethal doses of diamorphine (medical-grade heroin), after which he falsified their death certificates to indicate they had died of poor health.

Suspicions were raised as the number of his patients dying was very high, as were the number of cremation orders his colleagues were being asked to countersign.


Given the patients he killed were largely in good health, misguided “altruism” cannot explain his crimes.

Niels Högel, a German nurse, is another example. In 2019, Högel was found guilty of using lethal injections to murder 85 of his patients, some of whom he attempted to resuscitate to show off to his colleagues.

Medics who murder are rare.

The reason the Letby case (like Shipman’s before it) is causing such significant public interest and horror is because we see medics as trusted professionals.

We put our lives in their hands, and cases such as these cause significant fear when one is found to have breached that trust so fundamentally.

But it’s important to acknowledge they also cause such interest precisely because they are so rare.

While medics who turn serial killer are incredibly prolific, we should not fear unnecessarily for ourselves or our loved ones.

If you are concerned about a medical professional, you should report them to the appropriate authority. High-profile cases such as Letby’s have shown these individuals can be caught and their patterns of behaviour can be identified, and in that way we can protect the most vulnerable among us.The Conversation


Xanthe Mallett, Forensic Criminologist, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Feature image: The Conversation

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