Dr. Carolyn Rogers testified Tuesday at the coroner's inquest into Smith's death that waiting until the teen stopped breathing was too big of a risk to take.
Smith was 19 when she died at the Grand Valley Institution in Kitchener, Ont., in October 2007, after she tied a piece of cloth around her neck while guards, who were ordered not to intervene, stood outside her cell door and watched.
Rogers, who was Smith's physician during her time at Grand Valley, said it had become routine for Smith to use ligatures in full view of the guards.
She said she could see the prison system wasn't working for Smith, but she genuinely thought she could help keep the teen alive.
"You know she … she'd been doing this for so long, and … I really thought that we were keeping her safe," Rogers said.
She said she only found out after Smith's death about what has become the most disputed element of the inquest — the order that guards stay out of the teen's cell unless she stopped breathing.
"I felt like I'd been kicked in the stomach, I felt I was going to throw up. I just couldn't believe anybody would have made that order," said Rogers, who has been practising medicine for more than a decade.
"If there's a ligature around her neck, you have to go in and take it off. Waiting until you think she's in physical distress is completely inappropriate," she said.
"Once someone is in distress, you have no way of knowing how much time you have. If someone stops breathing, basically they are dead."
The Ontario coroner's inquest into Smith's death started on Jan. 14 in Toronto.
Earlier this month a senior official with Corrections Canada said previous witnesses misunderstood his direction to not enter Smith's cell if she was breathing.
Eric Broadbent, the prison manager, said the order was to focus more on Smith's level of distress than about her ability to breathe.
He said it was up to staff to decide and justify whether entering Smith's cell was warranted. He asked the guards to consider alternatives first, he said.
But corrections manager Heather Magee told the jury that staff at the institution were overwhelmed by instructions on how to deal with Smith, describing some of the orders as inhumane.
Magee apologized to Smith's family from the stand. "I am truly sorry to the family, I really am. And I can't imagine what that was like for them to go through," she said.
Magee said it was difficult to see guards, who were instructed to stay out of Smith's cell until she stopped breathing, penalized for following the orders of regional supervisors.
She told the inquest that it wasn't until Smith's death that management stepped up and brought in the extra resources guards had been asking for.
"All of the sudden, we had whatever we wanted," Magee said.