Three former members of the senior leadership team at the hospital where Lucy Letby killed babies have been arrested on suspicion of gross negligence manslaughter.
The three people, who have not been named, were in leadership roles at the Countess of Chester Hospital in 2015 and 2016 when the killer nurse carried out her crimes.
They have since been released on bail pending further inquiries. Cheshire Police said the case does not have any impact on Letby's 2023 convictions.
Letby, 35, was found guilty of murdering seven children and attempting to murder seven more between June 2015 and June 2016 while working in the hospital’s neonatal unit.
She is seeking to overturn her 15 whole-life orders at the Criminal Cases Review Commission having lost two legal challenges at the Court of Appeal.
Following her convictions, Cheshire Police launched an investigation into corporate manslaughter at the hospital amid allegations bosses breached their duty of care by ignoring signs Letby was harming babies.
The investigation was widened in March this year gross to include gross negligence manslaughter.
Corporate manslaughter focuses on systemic failures within an organisation, in this case Countess of Chester Hospital NHS Foundation Trust, while gross negligence manslaughter targets an individual's egregious lack of care that led to someone’s death.
Detective Superintendent Paul Hughes, Senior Investigating Officer for Operation Duet, said: "In October 2023 following the lengthy trial and subsequent conviction of Lucy Letby, Cheshire Constabulary launched an investigation into corporate manslaughter at the Countess of Chester Hospital.
"This focuses on senior leadership and their decision making to determine whether any criminality has taken place concerning the response to the increased levels of fatalities.
"In March 2025 the scope of the investigation widened to also include gross negligence manslaughter.
"This is a separate offence to corporate manslaughter and focuses on the grossly negligent action or inaction of individuals.
"It is important to note that this does not impact on the convictions of Lucy Letby for multiple offences of murder and attempted murder.
"As part of our ongoing enquiries, on Monday, June 30 three individuals who were part of the senior leadership team at the CoCH in 2015-2016, were arrested on suspicion of gross negligence manslaughter.
"All three have subsequently been bailed pending further enquiries.
"Both the corporate manslaughter and gross negligence manslaughter elements of the investigation are continuing and there are no set timescales for these.”
Cheshire Police said it is also carrying out a separate investigation into deaths and non-fatal collapses of babies in Chester and in the Liverpool Women's Hospital, where Letby trained for periods, going back to 2012.
"Our investigation into the deaths and non-fatal collapses of babies at the neo-natal units of both the Countess of Chester Hospital and the Liverpool Women's Hospital between the period of 2012 to 2016 is also ongoing”, Det Supt Hughes said.
A spokeswoman for CoCH reiterated it "would not be appropriate" for the hospital to comment due to the Thirlwall Inquiry - the public inquiry looking into how serial killer Lucy Letby was able to commit her crimes and “the ongoing police investigations”.
Lady Justice Thirlwall is due to publish the findings from her public inquiry in early 2026.
Letby's barrister Mark McDonald said the police's latest announcement has come at a "very sensitive time" and that a proper and full public inquiry into failings by the hospital is needed.
He said: "Yet another press release from the police at a very sensitive time when the CCRC (Criminal Cases Review Commission) are looking at the case of Lucy Letby.
"Despite this, the concerns many have raised will not go away, and we will continue to publicly discuss them.
"The reality is that 26 internationally renowned experts have looked at this case and the lead expert has concluded that no crime was committed, no babies were murdered.
"What is needed is a proper and full public inquiry into the failings of the neonatal and paediatric medical care unit at the Countess of Chester hospital."
