Justice Margaret Cameron says no one should assume that she 'by magic' knows how the system of health administration works. (CBC)

The judge leading Newfoundland and Labrador's breast cancer inquiry has made a plea for witnesses to step up with advice on how to prevent mistakes in the future.

Margaret Cameron made the plea Friday afternoon directly to John Abbott, the former deputy minister of health, but worded it clearly to apply to other witnesses called to the inquiry, which is investigating what went wrong with hundreds of hormone receptor tests, and what officials did after learning of the mistakes.

Abbott, who is scheduled to resume testimony on Monday, had bristled when co-counsel Bern Coffey asked if he had advice for the inquiry on how things could have been done better in dealing with Eastern Health, an authority that operates at arm's length from government.

Cameron, though, intervened after a government lawyer said Abbott had answered Coffey's questions.

"If he chooses not to give me his best advice, that's fine, but frankly, this whole thing would have been for naught unless I can come up with recommendations which are useful and can work in a practical way within the system," said Cameron, adding that Abbott is a valuable witness because he understands how government works.

"I am hoping nobody is assuming that by magic I somehow know how the Department of Health and how Eastern Health work on a practical level, because if the recommendations coming out of this commission do not work on the ground, then we will have been here for months and months and months for nothing," Cameron said.

"That's the point of the question. It's not what you would have done, so much as looking at, 'Are there better ways of doing it?'"

In a further exchange, Abbott held to his point of view that the department — which sets policy, while Eastern Health and other regional authorities are responsible for delivering services — had to "be careful of crossing the line, as it were" into Eastern Health's territory.

Abbott testified that while he felt that Eastern Health should have notified patients soon after learning of lab mistakes in 2005, he said it was not the Health Department's place to do so.

The public did not learn of problems with the lab until a report in the weekly Independent newspaper in October 2005.

Cameron, who sits on the Newfoundland Supreme Court's appeals division, began hearing evidence in March. The inquiry has largely focused so far on how Eastern Health and government officials dealt with the problem in 2005, in the wake of the first retests of samples taken from breast cancer patients.

This winter, the Newfoundland and Labrador government disclosed that 383 breast cancer patients had received inaccurate results for their hormone receptor tests, which are used to identify whether a patient can benefit from an antihormonal therapy like Tamoxifen. Of those, 108 patients had died. The inquiry has not been advised on whether any of the patients would have had different outcomes if they had received accurate results.