A lawyer defending Lucy Letby on Thursday handed over “fresh” medical evidence to an independent body aimed at clearing the name of the former nurse, whose convictions have made her the most prolific child serial killer in modern UK history.

Letby, 35, is serving 15 whole life sentences for the deaths of the babies at a neo-natal unit in the northwest of England where she worked between 2015 and 2016.

Letby was convicted of murdering seven newborn babies and attempting to kill seven others at the Countess of Chester Hospital neonatal unit.

Her lawyer Mark McDonald delivered the findings of a 14-strong international panel of neonatologists and paediatric specialists to the offices of the Criminal Cases Review Commission (CCRC), which investigates potential miscarriages of justice.

The CCRC has the power to refer cases back to the Court of Appeal if it determines there may have been a miscarriage of justice.

The doctors, all leaders in their field who reviewed the evidence without payment, presented their findings in London in February.

“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,” said retired Canadian doctor Shoo Lee.

Letby, who has always maintained her innocence, was accused of attacking the babies by various means, including insulin poisoning and injecting air into their bloodstreams which caused an air embolism that blocked the blood supply and led to sudden and unexpected collapses.

McDonald will also deliver a separate report to the commission’s offices in Birmingham from seven other medics which claims the results of insulin tests on two infants were unreliable.

One test used in both cases “can give rise to falsely high insulin results” due to the presence of antibodies which can interfere with the outcome, the medics say in the new report.

“Our inescapable conclusion is that this evidence significantly undermines the validity of the assertions made about the insulin and C-peptide testing presented in court.”

McDonald said the two reports constituted “fresh evidence” that “totally undermines the prosecution case at trial”.

Letby lost two bids last year to challenge her convictions at the Court of Appeal.