Police are investigating claims a mum died after doctors gave her an accidental paracetamol overdose in hospital.
Laura Higginson, 30, from Widnes, was being treated for suspected pneumonia when she died at Whiston Hospital in Merseyside in April 2017.
Mrs Higginson's husband Antony claims he only discovered months after her death that his wife, who had a rare genetic condition called Gitelman syndrome, had been given an overdose.
A spokeswoman for St Helens and Knowsley Teaching Hospitals NHS Trust said it accepted Mrs Higginson had been given a paracetamol overdose, but "expressly denied" it had caused or contributed to her death.
On Thursday, an inquest into her death was opened and adjourned to a date to be fixed, Sefton, Knowsley and St Helens coroner's office said.
John Doyle, principal lawyer at Slater and Gordon, which is representing the family, said: "The trust have now, after three years, admitted that administering the paracetamol overdose was negligent, however they continue to deny it caused or contributed to Laura's death.
"Independent expert evidence we commissioned was provided to the coroner and we welcome her decision to open the inquest."
A Whiston Hospital spokeswoman said: "The trust offers its sincere condolences to the family of the late Mrs Higginson.
"Following her death, an immediate and thorough investigation was carried out.
"The findings of independent clinical experts do not concur with the views of Mr Higginson and will be presented to the coroner during the inquest."
A Merseyside Police spokeswoman said: "We can confirm that an investigation is currently under way following the death of Laura Higginson at Whiston Hospital on April 19 2017.
"As such it would not be appropriate to comment further at this time."
