Since mid-2016, Deputy Coroner Anthony Schapel has been looking into the deaths of leukaemia patients Christopher McRae, Bronte Higham, Carol Bairnsfather and Johanna Pinxteren.

All four were among 10 patients who were underdosed during their chemotherapy treatment at the RAH or at the Flinders Medical Centre between July 2014 and January 2015.

But last week, on the day the inquest was due to hear closing submissions, some doctors argued Mr Schapel did not have the necessary jurisdiction to conduct an inquest, questioning whether the deaths were reportable under state legislation.

At a hearing on Wednesday, government counsel argued that any interpretation of the coroner's discretion to call an inquest should be broad.

The court was told that the question of whether the deaths were reportable should be determined at the start of the inquest and once determined, the court had a duty to proceed.

Counsel said it was often the case that there were many causes of death and it was only necessary for any one of them to be unknown to enliven the court's jurisdiction.

One of the surviving patients to be underdosed, Andrew Knox, described Wednesday's hearing as a very serious day for public trust in the medical profession.

He said he hoped the coroner would continue with his inquiry and come to "logical" findings of how the errors were made and how the situation was handled.

"In my view, we had options that could have saved lives and could have saved me a lot of suffering," he said.

The hearing was continuing with the coroner expected to reserve his decision on the application.

Australian Associated Press