Baby-killer Lucy Letby's conviction questioned after unearthed papers show she was off duty for third of cases

This shocking revelation indicates that the jury at Manchester Crown Court might have been misled over key evidence in the case against the nurse, who is currently serving 15 life sentences for murdering seven babies and attempting to kill seven more between 2015 and 2016.

This evidence directly contradicts a key prosecution argument presented by Nick Johnson KC, who told the jury Letby was "the one common denominator" in unexpected deaths or collapses.

The correlation between Letby's presence and the incidents became central to securing her conviction, due to the absence of forensic evidence or clear motive.

Canadian neonatologist Dr Shoo Lee is set to hold a press conference on Tuesday to challenge how his 1989 research on air embolism was used during Letby's trial, and is set to argue that none of the skin discolourations described in the babies' cases matched those typically seen with air embolism.

The respected medic is expected to say that air embolism, being a "very rare and specific condition", should not have been diagnosed in these cases merely by ruling out other causes of death.

Letby's original defence team did not call Lee to dispute the prosecution's claims, and the Court of Appeal later refused to allow him to clarify his research's interpretation.

Lee has revealed plans to present findings from an independent review conducted by a "blue ribbon committee" of 14 international medical experts into the deaths of the 17 babies Letby was accused of harming.

The experts are expected to challenge the official causes of death, with sources suggesting they reached different conclusions in potentially every case.

"This is not fair, because the evidence that was used to convict her, in my opinion, wasn't quite right," Lee told The Sunday Times.

"What I can say is that we looked at the cases in great detail and we came to very definite conclusions about what happened in every case," the 67-year-old expert added.

Former Cabinet Minister David Davis has called for a retrial, describing Letby's conviction as a "clear miscarriage of justice" as he claimed that police and the Crown Prosecution Service are withholding key evidence that could help Letby's case.

Davis has also highlighted hospital notes regarding Baby O, with consultant Dr Stephen Brearey's "sub-optimal care" allegedly contributing to the death after inserting a needle into the wrong side of the child's abdomen.

The note said that this was "undoubtedly a significant contributory factor in the baby's death, if not the outright cause".

Additional questions have emerged about Dr Dewi Evans, a key prosecution witness in the case. Appeal Court judge Lord Justice Jackson wrote to the trial judge explaining how Evans' report in an unrelated case had been dismissed as "worthless".

The judge claimed Evans had breached his duty as an expert by deciding on his desired outcome first, then "working out an explanation" to achieve it.

Dr Evans has responded that concerns about his evidence in the Letby trial were "unsubstantiated, unfounded, inaccurate", but declined further comment until the conclusion of Lady Justice Thirlwall's public inquiry.

A police spokesman said: "There is a significant public interest in these matters, however, every story that is published, statement made, or comment posted online that refers to the specific details of a live investigation can impede the course of justice and cause further distress to the families concerned."

The force emphasised that their primary focus remains on the families affected and the ongoing investigations.

A new legal team, led by criminal defence barrister Mark McDonald, has been instructed to take Letby's case to the Criminal Cases Review Commission.