Unmasked as the country’s most prolific child serial killer in modern history, faces dying behind bars.

But today, expert evidence was revealed which could mean she has been the victim of one of the greatest miscarriage of justice the UK has known. The 35-year-old ex-nurse is serving 15 whole-life orders after being convicted of murdering seven babies – and trying to kill seven others.

Now 14 experts have come forward casting doubt on her convictions, with the group’s chair Dr Shoo Lee declaring: “...we did not find murders. In all cases, death or injury were due to natural causes or just bad medical care.... In our opinion, the medical opinion, the medical evidence doesn't support murder in any of these cases, just natural causes and bad medical care."

But what was the evidence he presented?

The experts

Retired neonatologist Dr Lee disclosed the new medical evidence at a press conference in London today, said to be the result of the 14 world-leading experts' unanimous analysis findings. The panel, who worked pro bono. include members from six countries – Canada, the US, Japan, Germany, Sweden and the UK.

It comes after an academic paper Dr Lee co-authored over three decades ago was used to help convict Letby. But he has earlier reportedly told how the evidence “wasn’t quite right”. The assembled experts looked at all 17 babies Letby is accused of harming, in half a dozen different ways, he explained. In a forensic account, he today disclosed the findings of some of those cases.

Baby one

Dr Lee explained "baby 1" was alleged to have died from an injection of air. However, he said, in fact the baby died from thrombosis.

Baby four

In the case of "baby 4", he explained the allegation was that the infant was stable but on the third day collapsed due to an injection of air. But, Dr Lee said the baby died from "systemic , pneumonia and disseminated intravascular coagulation". "The mother should have received intrapartum antibiotics prior to delivery," he said. "There was delay in recognising respiratory distress after birth, there was delay in starting antibiotics and delay in starting treatment for the respiratory distress. We did not find any evidence of clear embolism."

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Baby nine

In the case of a child identified as baby nine, Dr Lee said her death was preventable – suggesting she had been poorly cared for. He added that there was no evidence of an air embolism, after claims Letby injected the child with air. He suggested the medics caring for her failed to respond timely to a bacterial infection with antibiotics, and concluded the child died from respiratory complications.

Baby 11

Baby 11 was born pre-term and resuscitated at birth, Dr Lee said. He said doctors took three "traumatic" attempts to insert an endotracheal tube. Dr Lee alleged the consultant who performed the procedure "didn't know what he was doing". He said when the consultant disconnected the endotracheal tube from the ventilator to manually resuscitate the baby with a bag, their chest did not move up and down - suggesting the tube was in the wrong place.

"The consultant therefore concluded and alleged that baby 11's first episode of clinical deterioration was caused by deliberate dislodgement of endotracheal tube because bagging failed to move the chest and carbon dioxide was not detected on capnography. He also alleged that the incubator alarms were deliberately turned off to prevent prompt rescue response because he did not hear the alarms when he entered the room."

But Dr Lee said there was a 94% leak of air with only 6% was going into the baby's lungs because the wrong sized intubation tube was used: "That's kind of like using a straw and blowing through a garden hose and hoping that you can inflate something at the end of the garden hose.

"It doesn't work and, as a result, ventilation was ineffective, because 94% of the air was leaking out and only 6% was entering the lung. Effective gas exchange could not occur, and mechanical ventilation could not generate sufficient pressure to keep the small air spaces in the lung open. When the tipping point was reached, the baby decompensated, desaturated and collapsed."

Baby six

Dr Lee then moved to baby six, a boy who survived after allegedly being injected with insulin. He said the child had been given the "wrong treatment" and he had been medically "mismanaged", adding his supposed high insulin levels due to injection by Letby had been misinterpreted.

Baby 15

The press conference heard that baby 15 was a boy, the second of pre-term triplets to be born by emergency caesarean. Dr Lee said the baby deteriorated and later died, with a post-mortem examination showing a ruptured haematoma of the liver, with prosecutors alleging he suffered blunt trauma to the abdomen.

"Later the accusation was then changed to say that in fact, there was deliberate injection of air into his intravenous system to cause air embolism, collapse and death," Dr Lee said, adding that he believed the haemorrhage was caused during birth as another triplet suffered the same issue. "It was highly likely that this was the result of extremely rapid delivery and this is a well-recognised cause of birth injury," he said. "One of the other triplets also had the same haematoma, although it was not this severe. The fact that two of them had the same problem again confirms that this was likely caused by birth injury."

Baby seven

In the final case highlighted during the press conference, Dr Lee told how baby seven was born very premature and had a lot of "chronic problems". At 14 weeks old the baby suddenly became unwell and the allegation against Letby was that the baby was overfed but later recovered, Dr Lee explained. But he said the evidence his team had found suggested the baby was in fact suffering from a viral infection.

"At Alder Hay Hospital she received seven days of antibiotics and she recovered after seven days, which is consistent with an infection," Dr Lee said. "In our opinion baby 7 had vomiting and clinical deterioration because of infection, possibly enterovirus infection, which can cause all these signs and symptoms. There is no evidence to support an injection into the stomach of overfeeding."

What does it mean?

Tory MP Sir David Davis described Letby's convictions as "one of the major injustices of modern times". And Mark McDonald, the barrister leading Lucy Letby's legal team, called today’s presentation as a "gamechanger". Asked what he thought of the press conference, he said: "I've never known anything like it. You know, never before – and I mean it's a grand statement to make – but never before have we had such an experienced credible body of experts come together across the and say something has gone wrong, and I think it's a gamechanger."

Criminal Cases Review Commission

Letby's case will be reviewed by the Criminal Cases Review Commission, which probes potential miscarriages of justice, after her lawyers made an application to the body on Monday. Asked whether Sir thought she was guilty, the PM's official spokesman said: "This was a truly horrendous case that shocked the nation. A criminal trial has taken place and Lucy Letby was found guilty.

"There is, of course, an established process through the Criminal Cases Review Commission, which is independent of Government, and the commission has today confirmed they have received an application from Ms Letby's legal team. We wouldn't get drawn on that independent process."

Case for the prosecution

Letby used a variety of methods to secretly attack a more than a dozen babies on the neonatal ward at the Countess of Chester hospital between 2015 and 2016. Seven of them died as a result, and a jury later found Letby guilty of their murder.

During the trial, Crown Court heard that doctors at the hospital began to notice a significant rise in the number of babies who were dying or were unexpectedly collapsing. When they were unable to find a medical explanation, police were alerted and an investigation followed.

Letby was first arrested in July 2018 and charged in November 2020. The prosecution was able to show evidence of Letby using various methods to attack babies, including: the injection of air and insulin into their bloodstream; the infusion of air into their gastrointestinal tract, force feeding an overdose of milk or fluids, and impact-type trauma. She was found to have killed the babies while deceiving her colleagues into believing there was a natural cause.

Letby lost two bids last year to challenge her convictions at the Court of Appeal - in May for seven murders and seven attempted murders, and in October for the attempted murder of a baby girl which she was convicted of by a different jury at a retrial.

At the first of those appeals, a bid to admit fresh evidence from Dr Lee was rejected, as three senior judges concluded there had been no prosecution expert evidence diagnosing air embolus solely on the basis of skin discolouration. Dr Lee said he has recently updated his academic paper and found no cases of skin discolouration linked to air embolism by the venous system.