Letby, 34, was found guilty of murdering seven children and attempting to murder seven more between June 2015 and June 2016 while working in the neonatal unit of the Countess of Chester Hospital in Chester, northern England.
Her case shocked Britain and prompted the government to order an inquiry, which will investigate the hospital and its response to concerns raised about Letby before her arrest.
The public inquiry will also look at the circumstances surrounding the murders and attempted murders committed by Letby, including whether governance contributed to the failure to protect babies.
It will start in Liverpool on Tuesday with opening statements from lawyers working for the inquiry followed by lawyers representing the victims' families.
Its work begins as Letby has reportedly hired a new legal team, with her lawyer Mark McDonald telling the BBC that "there is a strong case that she is innocent".
Lawyers representing some of the victims' families, however, say the speculation about her guilt or innocence, some of which has taken place on social media, has been distressing.
Prosecutors said Letby injected the infants with insulin or air or force-fed them milk, and a handwritten note found at her home after she was arrested stated: "I AM EVIL I DID THIS".
She was sentenced to life without parole last year and in July was found guilty of a seventh charge of attempted murder, on which the original jury could not reach a verdict.
Letby has always denied harming any child in her care and - despite the jury's verdicts and the rejection of her bid to appeal - her case has become a cause celebre, based on criticism of medical and statistical evidence presented at trial.
