LUCY LETBY CASE ROCKED BY NEW INSULIN EVIDENCE — BUT THE CONVICTIONS HAVE NOT BEEN OVERTURNED

The controversial case of former neonatal nurse Lucy Letby has entered another dramatic chapter after fresh medical and statistical analysis challenged key evidence used at her trial.

Letby remains convicted and is serving 15 whole-life sentences for the murders of seven babies and the attempted murders of seven others. Her convictions have not been overturned. But her legal team is continuing to argue that newly available evidence raises serious questions about whether the verdicts are safe.

At the heart of the latest challenge is the evidence surrounding two babies whom prosecutors said were deliberately poisoned with insulin.

And this is where the case becomes particularly complicated.

THE INSULIN EVIDENCE THAT HELPED DRIVE THE PROSECUTION

At Letby’s 2023 trial, prosecutors argued that abnormal blood-sugar results in two premature babies could only be explained by the administration of insulin.

The prosecution presented the laboratory findings as powerful evidence of deliberate poisoning.

Those two cases were especially important because, unlike several other allegations that relied heavily on medical and circumstantial evidence, the insulin cases were presented as having laboratory evidence supporting deliberate harm.

But experts reviewing the evidence after the trial now argue that the scientific picture may not have been as straightforward as jurors were told.

 A NEW REPORT CHALLENGES THE PROSECUTION’S INTERPRETATION

In July 2026, Letby’s legal team submitted a 100-page analysis to the Criminal Cases Review Commission.

The report was authored by Neil Aiton, a consultant neonatologist, and Hilde Wilkinson-Herbots, an associate professor of statistics at University College London.

According to reporting about the document, the experts challenge evidence given by prosecution expert Professor Peter Hindmarsh, alleging errors and omissions in his interpretation of the insulin results.

The report also reportedly raises the possibility that other explanations for the babies’ insulin readings were not fully presented to the jury.

Importantly, however, the underlying report has not been publicly released in full, so claims about its contents should be treated carefully.

COULD THERE HAVE BEEN NATURAL EXPLANATIONS?

That question has become one of the most contentious parts of the appeal effort.

A separate peer-reviewed paper published in April 2026 examined insulin readings in premature and critically ill infants.

Researchers Geoff Chase and Helen Shannon argued that naturally occurring biological mechanisms could potentially produce insulin and C-peptide patterns that were previously interpreted as evidence of externally administered insulin.

Their work does not prove that the babies were not given insulin.

Instead, the argument is narrower — that the laboratory results alone may not establish deliberate poisoning as conclusively as the prosecution claimed.

That distinction is critical.

The new evidence does not amount to a court finding that Letby is innocent.

It represents a challenge to whether particular medical evidence was interpreted correctly.

 THEN THERE IS THE CCRC

The Criminal Cases Review Commission, or CCRC, is now examining Letby’s case.

The commission received her preliminary application in February 2025 and subsequently received multiple expert reports, written submissions and defence materials.

In February 2026, the CCRC publicly confirmed that its review was still underway.

The commission also made an important point:

It does not decide whether Letby is innocent or guilty.

Its role is to investigate potential miscarriages of justice and, where appropriate, refer a case back to an appellate court if there is a real possibility that a conviction might not be upheld.

That means the current review is not an exoneration.

It is an examination of whether the existing convictions should be reconsidered by the courts.

 MORE EXPERTS HAVE QUESTIONED THE ORIGINAL CASE

The insulin evidence is not the only part of the prosecution case facing renewed scrutiny.

An international panel of medical experts has previously challenged aspects of the medical evidence surrounding the deaths and collapses.

Statistical experts have also questioned the use of staffing rosters as evidence of a pattern linking Letby to the babies’ collapses.

These criticisms have fueled an increasingly fierce debate over whether the original investigation and trial properly accounted for alternative medical explanations.

But the prosecution’s case remains significant.

Letby was convicted after a lengthy criminal trial in which jurors heard extensive evidence concerning multiple babies, medical records, witness testimony and other circumstances surrounding the collapses and deaths.

Her convictions remain legally valid.

ANOTHER DEVELOPMENT COMPLICATES THE PICTURE

In January 2026, prosecutors also announced that Letby would not face additional criminal charges concerning a number of other baby deaths and collapses investigated by Cheshire Constabulary.

The CPS said the evidential test was not met.

After families requested a review of that decision, the CPS announced in August that its independent review had upheld the decision not to bring the additional charges.

Police have emphasized that this decision does not undermine the existing convictions.

Instead, it reflects a separate assessment of whether the evidence in those additional cases met the legal threshold for prosecution.

 BEHIND THE SCIENCE ARE FAMILIES WAITING FOR ANSWERS

The controversy surrounding Letby’s case has become a battle over medical evidence, statistics and the reliability of expert testimony.

But at the center remain the families of babies who died or suffered medical collapses.

For them, any suggestion that the convictions could be unsafe is deeply significant.

At the same time, Letby’s supporters argue that new scientific evidence deserves to be examined without assumptions about the original verdict.

That is precisely what the CCRC is being asked to do.

 WHAT HAPPENS NEXT?

For now, Lucy Letby’s convictions stand.

The CCRC has not announced that it will refer the case to the Court of Appeal.

It has not declared Letby innocent.

And the newly submitted expert reports have not resulted in her release.

But the scientific debate surrounding the insulin evidence has changed the conversation.

What prosecutors once presented as compelling evidence of deliberate poisoning is now being examined by independent experts who argue that alternative biological explanations deserve serious consideration.

The question is no longer simply what happened at the neonatal unit.

It is whether all of the evidence was interpreted correctly the first time around.

 THE QUESTION THAT COULD DEFINE LETBY’S NEXT LEGAL BATTLE

Was the insulin evidence truly proof of deliberate poisoning?

Or could the babies’ abnormal results have had medical explanations that the jury did not fully hear?

The CCRC is now examining those arguments.

And if the commission ultimately concludes that new evidence creates a real possibility that the convictions would not stand, the case could return to the Court of Appeal.

Until then, one fact remains unchanged:

Lucy Letby remains convicted.

New experts are challenging aspects of the medical evidence.

A fresh report has been submitted to the CCRC.

The review is ongoing.

And the next major development could determine whether one of Britain’s most controversial criminal cases enters yet another courtroom chapter.