An American doctor who says he doesn't believe in brain death will not be allowed to serve as an expert witness in the case of a woman whose family is fighting to keep her on life support after a Toronto-area judge found he could not be impartial.

"The very issue of this case is the determination of brain death," which Dr. Paul Byrne opposes, Ontario Superior Court Justice Lucille Shaw said Friday.

"In my view, Dr. Byrne is more of an advocate than an independent witness."

The finding has thrown a wrench in a legal challenge filed by Taquisha McKitty's family, who had called on Byrne to testify that the 27-year-old woman should not have been declared brain dead last month.

The family's lawyer, Hugh Scher, has asked for the case to be adjourned for 30 days so they can retain a different expert, possibly another doctor from the U.S.

Erica Baron, the lawyer representing the doctor who found McKitty to be brain dead, opposed the request, saying the family's counsel had weeks to reach out to experts after concerns were first raised about Byrne's eligibility.

When someone is disqualified as an expert, it does not usually give lawyers the right to seek another expert, Shaw said. However, the judge acknowledged the "extraordinary circumstances" of the case and agreed to adjourn it to Nov. 6.

Testifying on his qualifications earlier this week, Byrne told a Brampton, Ont., court he thinks brain death is a made up concept meant to facilitate the collection of organ donations.

He also said on the stand that he would never pronounce someone dead solely because their brain has stopped functioning, even though he recognized that is a respected medical opinion and legal standard in the U.S.

Stanley Stewart

McKitty's dad Stanley Stewart said last month that his daughter "needs to be treated like a patient and given the proper care." (Pelin Sidki/CBC News)

Treatments not 'standard'

Baron pushed to have him disqualified on the grounds that he has "a demonstrated bias" against using neurological criteria to determine death.

The science informing his opinions is highly contested and there is no evidence to support the treatments he is suggesting for McKitty, she said.

"None of these proposed treatments are standard of care for brain-injured adults in Ontario," much less those who have been declared brain dead, she said.

Hugh Scher, who represents the McKitty family, had argued Byrne's opinions stemmed from his own observations of McKitty, his reading of her medical chart and his overall experience as a doctor.

The lawyer also noted Byrne has served as an expert witness in some cases in the U.S., which he said shows the courts there believe him to be qualified.

Taquesha McKitty

Taquisha McKitty is seen here with her daughter. (Instagram)

Kept on a respirator

McKitty was admitted to hospital in mid-September after overdosing on drugs and was declared brain dead days later after her condition worsened and she stopped breathing on her own, court has heard.

Her family obtained an injunction to keep her on a respirator and conduct more medical tests while it challenges that decision. It now seeks to further extend the injunction.

The family had filed a motion to have McKitty filmed for 72 hours to assess whether her movements were simply reflexes or something more, but Friday's ruling has left it in limbo.

The doctor who deemed McKitty to be brain dead testified Tuesday that the movements should not be interpreted as a sign of life.

Dr. Omar Hayani also told the court that the tests requested by McKitty's family are not the standard of care for patients like her and would have been "clinically not helpful" in assessing her state.

Byrne, meanwhile, has said McKitty's movements "indicate that Taquisha is alive and not a dead body."