The prison guards’ decision not to intervene as Ashley Smith strangled herself in her cell was a “tragic mistake,” Canada’s correctional investigator said Tuesday.

Howard Sapers said the troubled teenager had harmed herself in custody “well over 100 times before,” and someone was always there to stop her.

“In every one of those incidents correctional staff had intervened and often saved her life by removing ligatures or stopping her behaviour,” Sapers told CTV’s Power Play. 

But on Oct. 19, 2007, “the decision had been made to try a different approach and it was a tragic mistake,” he said.

Smith, 19, died after tying a ligature around her neck at the Grand Valley Institution for Women in Kitchener, Ont., as guards watched her lying on the floor in her segregation cell and gasping.

The jury at a coroner’s inquest into Smith’s death watched a disturbing video Monday of the teen’s last moments  and efforts to revive her once the prison guards finally entered the cell.

Sapers, who titled his 2008 report on Smith’s case “A Preventable Death,” said Tuesday that correctional officers always have the responsibility to “preserve life.”

Staff who have dealt with Smith in various institutions were “concerned about her well-being, but not always feeling equal to the task of managing her,” he said.  

“Quite sadly, there are many offenders in the system, men and women, who self-harm,” Sapers said.

Many of them have a history of mental illness and are held in segregation cells for lengthy periods of time, he said.

“Ashley was an extreme case, but unfortunately not unique in terms of repeated incidents of self-injury.”

The guard who videotaped Smith’s final attempt to strangle herself told the coroner’s inquest Tuesday he was just doing his job and following orders.

Rudy Burnett, a fill-in guard, had just finished his shift at Grand Valley and was about to go home when an emergency call sounded.

When he arrived at Smith’s cell, Burnett said he was given a video camera and told to start recording.

"If an order is given to me and I don't agree with it, there's a grievance procedure," he told the inquest.

Burnett said he believed he had done nothing wrong, even after he was arrested and charged with criminal negligence and failing to provide the necessities of life. The charges against him and three other prison employees were later dropped.

Smith, originally from Moncton, N.B., was first jailed at 15 for throwing crab apples at a mail carrier. She was supposed to serve a short prison sentence but racked up numerous offences against correctional staff and remained in jail for more than four years.

Smith was transferred in and out of various institutions in five provinces before ending up at Grand Valley.

Sapers said there are still “many circumstances” of self-injury in prisons.

“We certainly haven’t seen the last death in custody as a result of self-harm or suicide,” he said. “These things will happen.”

But he hopes that the inquest into Smith’s death will lead to improvements in Canada’s correctional system and a “more robust response” to emergencies involving inmates.

With files from The Canadian Press