Attorneys for British nurse Lucy Letby are beginning proceedings to overturn her conviction for killing seven babies after a team of international experts who reviewed the evidence used against her at her trial ruled that none of them were murdered.

Lucy Letby was convicted of killing seven newborns and attempting to murder eight others between June 2015 and June 2016 while working in the neonatal unit at the Countess of Chester Hospital in Chester, northern England.

He was sentenced to 15 life sentences, with, therefore, no prospect of parole. The 35-year-old maintained her innocence throughout her trial and was not allowed to appeal the conviction.

However, since then, medical experts have raised doubts about her guilt and created the impression that the evidence relied upon by the prosecution was flawed.

Her lawyer Mark McDonald said the new medical findings of the panel of international experts “shatter” the entire case. “There is overwhelming evidence that the conviction is not safe … If the experts are right, no crime was committed.”

Lucy Letby’s defence has submitted a request to the Criminal Cases Review Commission, which is looking into possible miscarriages of justice.

At her trial, prosecutors said the nurse killed five newborn boys and two girls by injecting insulin or air into their blood or by forcing them to breathe milk.

However, University of Toronto professor emeritus and neonatologist Sue Lee, who complains that his research was misused at the trial, said during a news conference in London that a team of 14 international experts reviewed the medical evidence and ruled that it showed none of the babies were attacked.

Instead, they show medical errors and omissions at the hospital unit.

“In summary ladies and gentlemen, we found no murders. In all cases, the death or injury was due to natural causes or poor medical care,” said neonatologist Sue Lee.

A spokesman for the Criminal Cases Review Commission was unable to specify how much time would be required for the case review process.