A public inquiry into allegations of abuse of patients at Muckamore Abbey Hospital is under way.
The hospital is run by the Belfast Health Trust and provides facilities for adults with special needs.
With the terms of reference agreed, the inquiry panel will begin trying to establish what happened between residents and some members of staff, and also examine management's role.
Seven people are facing prosecution. There have been more than 20 arrests.
It was announced in June 2021 that the inquiry will be chaired by Tom Kark QC, who played a key role in the 2010 inquiry into avoidable deaths at Stafford Hospital in England.
Speaking on Monday, Mr Kark said it was a "significant date for all those patients and families who have been affected by the issues under examination by the inquiry, many of whom have campaigned very hard to ensure this inquiry takes place".
"I want to reassure you that a thorough and impartial investigation will be carried out by the Muckamore Abbey Hospital Inquiry," he added.
Source: BBC News, 12 October 2021