Murderer Lucy Letby may have been motivated by a “pathological desire for attention and sympathy”, a criminology expert has said.

Dr Dominic Willmott, a senior lecturer in criminology at Loughborough University, said the former nurse’s text messages showed she wanted to “garner sympathy” from colleagues after the children’s deaths.

The expert told how there were “clear similarities” with the Letby case and historic cases of killer nurses, such as Beverley Allitt from the UK and Charles Cullen in the US.

Allitt, 54, targeted 13 victims during a 59-day spree which saw her kill four babies and poison nine others at Grantham and Kesteven Hospital, Lincolnshire, in 1991.

Doctors believe she suffered from Munchausen syndrome by proxy while carrying out the attacks, in which a caregiver may harm someone in their care to get attention.

Cullen, 63, murdered dozens, possibly hundreds, of patients during a 16-year career spanning several medical centres in the American state of New Jersey.

Dr Willmott believes there are clear resemblances between the historic cases and that of Letby.

The criminologist, who has previously authored a paper on the Beverley Allitt case, said: “In our analysis of healthcare professionals who perpetrate violence against their patients, especially children, offending appeared to be motivated by a pathological desire for attention and sympathy emerging as a consequence of their involvement in the case.

“There was a complex interaction between this and a history of personality disorder diagnoses and characteristics, and were often found to be highly sadistic and narcissistic as described by those who knew them.”

Speaking after the trial, detectives said the reason why Letby went on a killing spree at the Countess of Chester Hospital neonatal unit may never be known.

Prosecutors never advanced a motive as they outlined the allegations against her to the jury at Manchester Crown Court.

Dr Willmott said Letby’s interaction with colleagues was indicative of her desire for “sympathy”.

He continued: “Text messages released during the Letby trial appear to indicate her efforts to garner sympathy from her colleagues following the children’s deaths.

“Other evidence that she had to be repeatedly asked to focus on other patients around the time of the death of other babies and her passing on death notifications to family members seems to indicate her desire to be personally involved in the case, even when doing so was likely to raise suspicions about her involvement.

“My heart goes out to the families whose babies were mercilessly taken from them.”

James Treadwell, professor in criminology at Staffordshire University, also said he believes there are similarities between Letby and Allitt.

Prof Treadwell suggested a number of reasons why Letby could have committed the crimes, including that she is a narcissist; Munchausen syndrome by proxy; she enjoyed the risk; she used the offences as a means for attention from the doctor prosecutors said she had a “crush” on; or evil.

But the expert said he thinks that answering “how” is much more important than the “why” question – which he believes will never be answered – as finding out how could prevent it happening again.

Sometimes those who do the most evil acts can be remarkably beige

Prof Treadwell said: “The police described her as beige but beige people can do evil acts as well, it’s not that it always comes from the people that radiate malice.

“Sometimes those who do the most evil acts can be remarkably beige.”

He added: “One of the things that is quite interesting is she is being compared in the media more to Myra Hindley and Rose West, but Beverley Allitt is often forgotten as a serial killer, people don’t remember her.

“We can suggest conditions like Munchausen by proxy and narcissism, it could simply be that there’s an element of enjoying the risk.

“I saw suggestions that she had an infatuation with one of the doctors, it could simply be that harming the children could not have been significant in her thought process, that it would be a vehicle for something else.

“Is there evil? I’ve never believed that people are evil, some will do evil acts and many are capable of doing evil acts.

“All of these things are possible in the case of Letby, I think the problem is, will people ever know.

“We’ll never be furnished with a ‘why’ from her, she’ll continue to protest her innocence.

“It’s with the ‘how’ question you can prevent these things happening again. We had Allitt and Harold Shipman in medical situations, if you don’t answer the ‘how’ question, tragic history, terrible history, bereaved families could happen again.”