"Bad practices" were allowed at Muckamore Abbey Hospital to "the terrible detriment of a number of patients", the chair of an inquiry into the Co Antrim regional facility has said.
Speaking on the first day of public sessions at the inquiry, Tom Kark QC said patients at the hospital were "highly vulnerable in different ways and it is understandable there is considerable public anger at some of what has been revealed".
The inquiry, which is expected to last for many months, is investigating the alleged physical abuse of vulnerable patients by staff at the hospital.
It will look at the care of residents and the role of management and oversight. It will also make recommendations to prevent a repeat of the scandal.
The probe will hear from key people including patients' parents, the Belfast Health and Social Care Trust which is in charge of the hospital, the Department of Health, the Regulation and Quality Improvement Authority (RQIA) and the PSNI.
The inquiry is running in parallel with a major police investigation - the UK's largest-ever probe into the alleged abuse of vulnerable adults.
Dozens of staff have been suspended. A total of 38 people have been told they are to be prosecuted in connection with the Muckamore probe.
Police have already trawled through thousands of hours of CCTV footage from the hospital.
Mr Kark said the panel will have to view CCTV footage in private at this stage due to the ongoing police investigation.
He said parents and carers had felt let down.
"Relatives and carers who entrusted their loved ones to the hospital to be cared for with compassion have discovered in many cases that's not what was happening," he said.
"And because so many of the patients were non-verbal or had difficulty expressing themselves they couldn't express what was happening or they were not regarded as credible.
"Many of the parents and carers who trusted the hospital have been let down. They are understandably furious and some feel guilty."
Mr Kark said he had met many families "who had expressed their great upset and anger at what they have now discovered was happening when they left their loved relatives at Muckamore".
"Their anger and upset is perfectly understandable," he said.
Mr Kark said the inquiry is the culmination of a "massive effort" by relatives and will scrutinise "what was happening at the hospital over many decades".
He said patients "who had been abused or received poor care" and their relatives or carers should be at the "front and centre" of the inquiry.
"Getting to the bottom of what's been happening at Muckamore would be quite impossible without hearing about the experiences of patients, either directly from those patients or their loved ones," he said.
Health minister Robin Swann announced in September 2020 that a public inquiry into the hospital would be held.
The scandal is the biggest public safeguarding case in the history of the health service.
Mr Kark, a senior English barrister who acted as Senior Counsel to the public inquiry into the failures at the Mid Staffordshire NHS Foundation Trust, is joined by fellow inquiry panellists Prof Glynis Murphy and Dr Elaine Maxwell.
Ahead of today's session, family members held up photos of their loved ones outside the inquiry building on Gordon Street in the Cathedral Quarter.
Some were visibly emotional before the landmark session began.
Mr Kark said the inquiry will be hugely important, not least to help the health service learn from any mistakes.
"The treatment and care of those with learning disabilities or those with mental illness, who are by their nature vulnerable, should be of a high quality and safe in any civilised society," he said.
"To abuse those people receiving such care is anathema to any competent and caring health professional.
"It brings the medical, nursing and care professions into disrepute and it makes people fearful of committing their loved ones to the care of others who should be able to care for them safely and with compassion.
"The management of such facilities should perhaps obviously of the highest standard.
"The practices of staff should always be under scrutiny, both internally and by external agencies, to ensure that high standards of care are being delivered and that all staff are behaving compassionately to even the most challenging of patients."
Mr Kark said Muckamore had been referred to as a "scandal".
He said that, without predetermining the outcome of the inquiry, "it is quite obvious that bad practices were allowed to persist at the hospital to the terrible detriment of a number of patients".
Mr Kark said the inquiry could not rule on anyone's civil or criminal liability but that would not prevent the panel from making conclusions "which may lay blame at an individual or organisation's door".
He said the inquiry "will inevitably take some time" but, if it comes across serious issues, it will write an interim report and make recommendations before the sessions end.
