A hospital in northwest England where a neonatal nurse was and trying to kill seven others is facing an inquiry into how so many newborns were harmed.
The investigation at the Countess of Chester Hospital begins Tuesday against a push by supporters of former nurse for a legal review of the evidence used against her.
But the inquiry being held in Liverpool won't review the legal basis for Letby's convictions. Instead, it will look at what failures led babies to repeatedly be harmed, how complaints by staff were managed, and how parents were treated.
It will also explore the culture within the National Health Service, which had a similar scandal when nurse Beverley Allitt was convicted of killing four infants and attacking nine others at Grantham Hospital in 1991.
"Everyone was determined that it would not happen again," said Justice Kathryn Thirlwall, an appellate judge leading the inquiry. "It has happened again. This is utterly unacceptable. I want to know what recommendations were made in all these inquiries, I want to know whether they were implemented? What difference did they make? Where does accountability lie for errors that are made?"
Letby, 34, was and attempted murder of six others -- including two attempts on one child. A case in which jurors couldn't reach a decision was retried and Letby was convicted in July of another attempted murder. She was sentenced to 15 life terms with no chance of release -- only the fourth woman in the U.K. to receive such a term.
Prosecutors said she harmed babies in ways that left little trace, including injecting air into their bloodstreams, administering air or milk into their stomachs via nasogastric tubes, poisoning them with insulin, and interfering with breathing tubes.
She was the only employee on duty in the neonatal unit when the children collapsed or died from June 2015 through June 2016. Prosecutors described her as a "constant malevolent presence."
Letby testified that she never harmed a child and still maintains she is innocent.
Although her appeals were rejected, another lawyer hopes to bring new evidence before the Criminal Cases Review Commission, or CCRC, which looks into possible injustices and could trigger an appeal.
A growing number of supporters have rallied to her cause, particularly after a lengthy New Yorker in May raised doubts about the circumstantial and statistical evidence used against her.
A group of scientists, doctors, and legal experts sent a confidential letter to Britain's ministers of health and justice, asking to postpone the inquiry or look at a broader range of factors that led to the deaths of babies, "without the presumption of criminal intent," at the hospital.
The group that independently reviewed scientific evidence at Letby's trial warned legal systems were "particularly vulnerable to errors" when dealing with technical matters, "especially in cases involving statistical anomalies in healthcare settings."
Numerous scientists have criticized the prosecution's use of a chart showing Letby was always on shift when babies collapsed or died. In comparison, the chart showed that each of the other 38 nurses on staff were on staff only a few times when the babies were in danger. The chart also didn't include the deaths of babies for which Letby wasn't accused of murdering.
"It looks like a very dramatic and suspicious coincidence that Lucy Letby was on shift every time something happened to a baby," said Peter Green, a statistician at the University of Bristol. "But you could take other data and make a chart like that for any other nurse at the hospital."
Green co-authored a report for the Royal Statistical Society that said improperly interpreted statistics could make it appear some health workers were serial killers. Their concerns were triggered partly by a similar case in the Netherlands, involving a pediatric nurse named Lucia de Berk, who was later exonerated after being convicted of the murders of four children and the attempted murders of three others in 2004.
Sarrita Adams, a forensics biotech consultant in the U.S., began following the case against Letby when some of the scientific evidence sounded "really far-fetched."
Adams' organization, Science On Trial, reviewed available scientific data presented against Letby and produced a nearly 200-page report.
The contention by the prosecution's lead medical expert witness, Dewi Evans, MRCP, that Letby hurt some of the babies by injecting air into their veins or stomachs, creating an air embolism, strained credibility, Adams said. Evans' contention relied on a 1989 research paper describing how high-pressure oxygen delivered to the lungs can cause an air leak and isn't comparable to someone injecting air into a vein.
"These are completely different things and it is bizarre that was accepted as a plausible way to kill these babies," she said.
The author of the 1989 research paper later testified that his study had been misinterpreted, explaining that none of the babies Letby was accused of killing had skin discoloration associated with an air embolism. Still, the prosecution argued that since the author hadn't been privy to the babies' medical records, he wasn't qualified to speculate on how they died.
Adams and others were also concerned about other relevant context that appeared to be left out during the trial.
For example, experts for the prosecution testified that the death rate at the chronically understaffed hospital where Letby worked rose during the 2 years when the seven babies she was convicted of killing died. But mortality continued to increase even after Letby was no longer working there.
Challenges to Letby's convictions have unnerved the families of the children killed or injured, several of whom are living with permanent consequences.
"The families are devastated by the reporting at the moment," attorney Tamlin Bolton, who represents the families of six victims, told BBC Breakfast. "It is the families that are going through this, continuing to go through this in its enormity and sincerity."