A public inquiry into how Soham killer Ian Huntley got a school caretaker job will ask "tough" questions, the man leading it has said.
Huntley had been investigated several times
Huntley was convicted at the Old Bailey in December of murdering Holly Wells and Jessica Chapman.
Many were shocked when it emerged he got his job despite a string of underage sex allegations against him.
Ex-civil servant Sir Michael Bichard opened the inquiry in London with a moment's silence to remember the two girls.
Sir Michael, who was appointed by Home Secretary David Blunkett, said the inquiry was not a trial or disciplinary hearing.
But he said: "Inevitably my task will involve asking some tough questions and perhaps criticising individuals and organisations.
"You can be sure I will not shirk from that if I consider it to be justified and necessary."
He said his aim was "to discover first what happened,
secondly why it happened and thirdly what lessons can be learned".
SIR MICHAEL BICHARD
Worked 20 years in local government, then 10 years in Whitehall
Last post was as top civil servant in Department for Education and Employment
Previously chief executive of Brent and Gloucestershire local authorities
Also served as chief executive of Benefits Agency
Left civil service May 2001 and later appointed rector of London Institute
Knighted in 1999
Married with three children
Sir Michael will examine how police intelligence was handled, vetting practices and why information was not shared between agencies that dealt with Huntley.
The girls' families were not at the inquiry's opening but Humberside
and Cambridgeshire police were represented.
Three weeks of public hearings will begin on 16 February.
After Huntley received two life sentences for murder it emerged he had faced previous accusations of rape, indecent assault and underage sex on a number of occasions in or near Grimsby.
Despite having been investigated by the police on several occasions, he was not stopped from joining Soham Village College by those responsible for vetting.
Both Cambridgehire and Humberside police told the inquiry they would co-operate fully.
Jeremy Gompertz QC, for chief constable of Humberside David Westwood, said: "All relevant material will be disclosed. Mistakes will be acknowledged."
Simon Freeland QC, for Cambridgeshire Constabulary and the Cambridgeshire Police Authority, said they intended to co-operate in an "open and frank manner".
Ahead of the inquiry opening, Sir Michael said: "This tragic case has raised issues of significant public interest.
"There has been much media coverage and speculation as to what happened in respect both of Huntley and of the system more widely.
"I would assure those interested that I will be undertaking this inquiry in
an entirely objective and independent fashion."
Mr Blunkett has also asked Chief Inspector of Constabulary Keith Povey to
review Cambridgeshire Police's handling of the hunt for the girls' killer.