When Dr. Shoo Lee, one of Canada’s most renowned neonatologists, wrote an academic paper in 1989, he never imagined it would one day help convict a British nurse of murder.
But more than three decades after his paper was published, that is what happened.
Lucy Letby, a former nurse in a neonatal unit in northern England, was found guilty in two trials in 2023 and 2024 of the murder or attempted murder of 14 babies in her care, and sentenced to life in prison, where she remains today.
The case rocked Britain, seeming to expose a remorseless serial killer who, prosecutors said, used a bizarre range of techniques to kill her tiny, often very premature, victims: Injecting them with air, overfeeding them with milk or contaminating their feeds with insulin.
For seven of the murder or attempted murder charges, the prosecution’s lead expert witness relied on Dr. Lee’s 1989 paper on a rare complication in newborns — pulmonary vascular air embolism — to argue that Ms. Letby had intentionally injected air into their veins.
The only problem? The expert witness had misinterpreted his work, Dr. Lee says.
“What they were claiming was that this baby collapsed and had skin discoloration, therefore that equals air embolism,” said Dr. Lee, 68, in an interview in London last month. But, he said, “That is not what the research shows.”
That realization set Dr. Lee on a moral mission to review Ms. Letby’s case. Working pro bono, he gathered 14 specialists from around the world to assess the clinical evidence. Last month, he revealed their explosive findings — that “there was no medical evidence to support malfeasance causing death or injury” in any of the babies that Ms. Letby was charged with harming.
“If there’s no malfeasance, there’s no murder. If there’s no murder, there’s no murderer,” Dr. Lee said, adding, “And if there’s no murderer, what is she doing in prison?”
Ms. Letby has exhausted her avenues to appeal in the courts. Her only hope now lies with a small, independent body, the Criminal Cases Review Commission, which is responsible for investigating possible miscarriages of justice.
‘I didn’t know whether she was innocent or guilty’
Dr. Lee, who retired in 2021 to a farm in rural Alberta, knew almost nothing about Ms. Letby’s case until an email landed in his inbox in October 2023.
Ms. Letby had always maintained her innocence, and her lawyer wanted Dr. Lee to review the medical evidence. “I thought it was spam at first, because how often do you get an email like that?” Dr. Lee said. After a second email, he realized the request was real.
Dr. Lee had spent his entire career focused on the youngest patients. After completing medical school in his native Singapore, he moved to Canada and trained in pediatrics before undertaking a neonatal fellowship at Boston Children’s Hospital and later a Ph.D. in health policy at Harvard.
In 1995, he created the Canadian Neonatal Network, connecting specialists from across the country to improve outcomes for newborns. He became pediatrician-in-chief at Mount Sinai Hospital, Toronto, and in 2019, he received the Order of Canada for introducing best practices that reduced infant mortality.
As he studied Lucy Letby’s trial transcripts, Dr. Lee immediately knew his research had been misinterpreted. “I didn’t know whether she was innocent or guilty,” he recalls. “But regardless of whether you’re innocent or guilty, you cannot be convicted on wrong evidence. That’s just wrong.”
He agreed to help with Ms. Letby’s request for an appeal, writing to England’s Court of Appeal and later providing live video testimony. But the court ultimately denied her request, saying Dr. Lee’s testimony should have been introduced at trial.
It was then that Dr. Lee decided to assemble a team of neonatal specialists to look into the case.
“This panel, you’re not going to find a better group of people,” he said, rattling off a list that included the head of neonatology at Children’s Hospital of Philadelphia, a former president of Britain’s Royal College of Pediatrics and the former director of the neonatal intensive care unit of Boston Children’s Hospital.
The key caveat Dr. Lee insisted on was that the panel’s review would be released no matter their findings — even if they strengthened the case that Ms. Letby was guilty.
‘You’re going to get disasters’
The experts, who all worked on a voluntary basis, forensically assessed the cause of death or deterioration for each of the 17 babies whom Ms. Letby was initially charged with murdering or attempting to murder.
Two experts separately examined the medical notes of each baby. If their assessments differed, a third expert was brought in. The process was painstaking and took four months. But the final results were clear, Dr. Lee said. “In all cases, death or injury were due to natural causes or just bad medical care,” he told the news conference last month.
In the case of one baby, for instance, the prosecution argued at trial that she had been stable and had died from an injection of air into her IV line, causing an embolism. But the independent review found, based on her medical records, that she had died of sepsis and pneumonia, and that the mother, who went into labor prematurely, had not been given antibiotics to prevent infection.
In another case, a baby born at 25 weeks was intubated using the wrong size of endotracheal tube. While the prosecution alleged that Ms. Letby attempted to murder the infant by dislodging the tube, the experts found the baby’s condition deteriorated because of injury caused by intubation with a tube that was too large, and because a doctor did not understand “the basics of resuscitation, air leak, mechanical ventilation, and how equipment that were commonly used in the unit work.”
Some of the hospital staff, the panel concluded, were caring for the most critically ill or premature babies in a unit that was only meant to treat babies with lesser needs.
“You’re asking doctors in places without the expertise, without the infrastructure, to look after babies that they they’re not prepared to do,” Dr. Lee said. “And if you do that, then you’re going to get disasters.”
Nobody ever saw Ms. Letby harming a baby, and major questions were first raised about her guilt in a New Yorker article in May 2024. In the months since, dozens of experts in medicine and statistics have voiced concerns about the evidence.
Dr. Dewi Evans, the prosecution’s lead expert witness, did not respond to requests for comment, but he has publicly criticized the panel’s work and said he stands by his testimony.
The Countess of Chester Hospital, where the deaths took place, said it was focused on an ongoing police investigation and on a public inquiry that was set up by the government last year to investigate how a serial killer could get away with such crimes for so long. Earlier this week, the hospital’s former managers requested a halt to that inquiry, in the wake of Dr. Lee’s review, but the judge refused, saying that the inquiry was never focused on examining Ms. Letby’s guilt.
Mark McDonald, Ms. Letby’s current lawyer, plans to include Dr. Lee’s full expert report in his application to the Criminal Cases Review Commission, which can refer cases back to the Court of Appeal. The commission said in a statement last month that it had “received a preliminary application in relation to Ms. Letby’s case, and work has begun to assess the application.”
The mother of a child whom Ms. Letby was convicted of attempting to murder denounced the expert panel’s assessment, and a spokesman for the C.C.R.C. asked “that everyone remembers the families affected.”
Dr. Lee insisted that those families were one of his central concerns as he analyzed the cases, after spending four decades caring for babies.
“I can tell you one thing: Families want to know the truth,” he said. “They want to know the truth, regardless of whether it is painful or not painful. They want to know what really happened.”
