TORONTO -- A teenaged girl who killed herself in her prison segregation cell was one of the most difficult cases he had ever encountered, a psychiatrist testified Monday.

Dr. Jeffrey Penn told the inquest into her death that only the best quality, sustained psychological care might have helped Ashley Smith overcome her extreme problems.

"She presented one of the more severe personality pathologies than I have encountered," Penn said.

"She would have a period where she was making progress and then she would have to self-destruct."

Penn first encountered Smith, who was then 18, on Nov. 6, 2006, just days after she was transferred to her first adult prison: Nova Institution in Truro, N.S.

The psychiatrist, on a contract to provide services for a few hours a week at Nova, spent 35 minutes interviewing Smith through the food slot of her segregation cell -- something prison staff deemed necessary.

"This young woman is essentially a large tyrannical child who can't tolerate limits, feels estranged and isolated from peers, unloved, unliked, and often hopeless," Penn wrote at the time.

"At times, wants to be the best at being 'bad;' and is succeeding."

Penn described Smith as having a borderline personality disorder who exhibited self-harming behaviours and was at times suicidal.

She had been teased mercilessly growing up. She was emotionally immature, giggly, and showed sadistic tendencies with only a limited capacity for remorse, he said.

He prescribed sedatives to calm her down, and urged positive rewards for good behaviour.

Four days later, Penn saw her for 10 minutes -- again through the food slot.

"Ashley has been doing much better -- no major outbursts," he wrote.

The progress was short-lived. Smith smeared feces, grabbed and spit at guards, and abused herself and staff.

By mid-December, with Nova correctional staff at their wits' end, plans were made to transfer her to the Regional Psychiatric Centre in Saskatoon.

"It was a desperate situation. She was asking for more help. She said she was hopeless and was going to continue to act out to accomplish her goal of leaving Nova," Penn said.

"It was looking dark and very grim."

Penn testified he believed the Saskatoon facility would be able to offer Smith a higher level psychiatric service than Nova could, even if it meant distance from her mother in New Brunswick.

The inquest has previously heard from Allister Webster, a psychologist at Nova, who said he felt undermined and blindsided that Smith was transferred while he was on vacation.

Penn said he didn't know anything about that.

He next saw her when she returned a second time to Nova seven months later in late July 2007, after more than a dozen transfers between various prisons.

"Ashley was dour, sullen, blunted in general, with occasional bursts of animation and humour," he wrote.

He said he received no information on what had happened to her during her various placements, including at the Saskatoon centre.

"It would have been very useful to me," he said. "Certainly, I couldn't gather that information through the food slot."

Despite the various problems, Penn said the mental-health system in prison is "better than people think," although it could be improved.

Smith, however, was simply an extremely difficult inmate and patient.

"She had incredibly poor social skills. She can't get along with peers or with staff," he said.

"The answer was going to be very intensive psychotherapy, but where? I don't know."

Smith had a tremendous drive not just for attention, but also to control her world and her environment, Penn said.

She also had a strong need for arousal.

"When I'm bad, I get a feeling of excitement," he said she told him.

Within weeks, Smith ended up at the Grand Valley institution in Kitchener, Ont., where she choked to death in segregation in October 2007.

She was 19.