Blaine Phibbs, a correctional officer, testified he first saw Ashley Smith tie a ligature around her neck within 12 hours of her arrival.
He wasn't sure whether it was sheet or towel or how she got it, he said.
After that, Phibbs said, she would try to choke herself seven or eight times a day "on a bad day" — until she eventually used up all the ligatures she had hidden in a body cavity.
"That's when her behaviour got more positive," Phibbs said.
Smith needed support walking when she first arrived at Grand Valley Institution in Kitchener, Ont., in May 2007, and was immediately placed in an isolation cell.
It was one of her many transfers in the last year of her life.
"She appeared sedated. She was moving slower. She wasn't very talkative," Phibbs told the inquest into her death.
Smith's management plan called for her to be placed in segregation in a security gown with a security blanket and security pad. She was placed on 15-minute watch.
Soon after, however, she damaged the sprinkler head in her cell, causing flooding.
"She took it apart. She smashed it," Phibbs said.
"The noise was so loud."
The correctional officer also told jurors that Smith was inadvertently let out of her cell twice, when her door was opened by remote.
Jurors watched part of a lengthy video of one of the occasions, after Smith retrieved items from outside the cell before retreating back inside.
On Monday, jurors saw video of the frantic last-ditch efforts to save Smith, 19, of Moncton, N.B., who had tied a ligature around her neck and died in front of guards on Oct. 19, 2007.
Earlier Tuesday, the correctional officer who took the video testified about the shock he felt at finding himself at a police station under arrest, stripped of his shoes and facing charges in the tragic death.
Rudy Burnett said he felt as if he had been criminally convicted, even though he believed he had done nothing wrong.
"It was not a very nice situation. I was under a lot of stress. I was very agitated," he said.
The calm, soft-spoken Burnett, who now works at a halfway house for men, also testified about the difficulties of being a guard in the prison system.
Among other things, he said, he had witnessed serious assaults.
"It's very traumatic," he told coroner's court. "Over the years, you do sort of get desensitized."
He said he relied on family and church to help him keep a sense of himself.
Burnett, who was charged with criminal negligence and failing to provide the necessaries of life in Smith's death, was grilled about his reluctance to give police the names of the other guards present at her death.
His lawyer had advised him to say as little as possible, coroner's court heard.
Asked if prison guards were like a "fraternity" and he was trying to protect the others, Burnett said a fraternity conjured up an image of college hijinx.
"I really don't consider it a fraternity," he said. "More like a brotherhood."
Charges against Burnett, who had been pressed into videotaping the choking death of Smith in her cell in Kitchener, Ont., five years ago, were dropped.
He insisted he was just doing the job he was given and following orders to videotape.
In a perfect world, Burnett testified earlier, he would intervene to try to save a life but in the correctional world, it's a different story.
"If an order is given to me and I don't agree with it, there's a grievance procedure," he said at one point Tuesday.
Outside court, Smith family lawyer Julian Falconer said he had little sympathy for the guards who failed to save the teen's life.
"Human beings are human beings; good people do bad things," Falconer said. "On that day, a group of guards did bad things."
The inquest continues Wednesday.