The chair of England's first public inquiry into mental health deaths vowed to "seek out the truth" - despite difficulties getting documents from the NHS.
The first key evidence sessions in the Lampard Inquiry - examining more than 2,000 deaths at NHS inpatient units in Essex between 2000 and 2023 - have begun in London.
Baroness Lampard said although the hearing was "breaking new ground", 21 legal notices had been issued to NHS organisations to force them to submit evidence.
"We will seek out the truth," she said, adding she would not hesitate to use her legal powers "to the fullest extent necessary to compel the production of evidence where it's not provided".