Dr. John Carlisle rejected the physicians' argument that the inquest, set to begin in early 2013, would exceed its authority by calling witnesses from a number of prisons across the country.
Carlisle wants the inquest to have a broad focus, including a look into how the teenager was treated after repeated episodes of self-harm.
Smith was first charged with a criminal offence in March 2002 when she was 14 years old. Incarcerated at 15, her additional infractions while in youth custody racked up enough extra time behind bars that she eventually graduated to the federal adult prison system.
During the year she spent in federal custody, Smith was transferred 17 times between nine institutions in five provinces.
She died at age 19 while being held at the Grand Valley Institution for Women in Kitchener, Ont. She choked to death while prison guards — who were told not to intervene — watched from outside her cell.
Graphic videos show Smith's treatment
Recently released videos show some of the treatment Smith received in the months before her death. The videos show Smith being flown between facilities, wearing two mesh hoods to prevent her from spitting and with her hands duct-taped. Another video shows Smith tied to a gurney in a Quebec prison after she tried to cut herself in her cell.
The three doctors had argued that the inquest should not examine any events related to the case that occurred outside Ontario, or "which the legislature of Ontario is incompetent constitutionally to address."
At first, their position was supported by lawyers for Corrections Canada.
"This has become an investigation into how [Corrections Canada] treated Ms. Smith, and not an investigation into her death," correctional service lawyer Nancy Noble said. She said, Carlisle wants to turn the inquest "into full-blown inquiry into operations and management of [Corrections Canada]."
But, in November, the correctional service dropped their challenge of the inquest's scope.
"The stark videotaped evidence shamed the correctional service into doing the right thing," said Julian Falconer, lawyer for the Smith family. "One wonders what it would take for those doctors who treated Ashley Smith to feel the same sense of shame and allow us to get on with the inquest."
The inquest will proceed as planned, and Carlisle expects to begin calling witnesses early in the new year.