In the early morning of Aug. 8, 2009, a 16-year-old girl Whitehorse girl shocked herself and anyone who knew her by stabbing her mother's live-in ex-boyfriend to death.

When neighbours awoke to the news, they were dumbfounded.

Rumours swirled about drugs and sexual abuse – people dreamed up the extreme circumstances that would make an otherwise normal teenager take another person's life.

As the days wore on, no one close to the case could understand what had happened to make her kill the man.

There was no evidence of sexual or physical abuse, the girl wasn't high on drugs or driven by a need for money. She seemed mentally sound and had no criminal record.

She was a pretty typical teenager, dealing with issues that many young people face.

She was upset about a recent breakup with her boyfriend. She and her best friend smoked a lot of pot, dabbled in Ecstasy and drank. She was sometimes bullied at school and got into a couple of fights with the kids who picked on her and her friends.

She held down a part-time job and got passing grades at school.

Her mom was an alcoholic who would usually go out for a few drinks after work, come home, drink some more and pass out on the couch. The house the family lived in was small and poorly maintained.

Most importantly, the girl hated sharing her home with her mother's middle-aged ex-boyfriend, who did little more than sit in his chair in the living room, smoking cigarettes and drinking.

He had been living with the family for about five years, and for most of that time was unemployed and contributed no money and little work to the household. Her mother bought him his beer and his cigarettes.

He was described as sickly and mean-spirited.

The girl's mother had stopped having a romantic relationship with the man years earlier, but every time she asked him to leave, he made an excuse or simply ignored her eviction notices.

He was passive aggressive, the mother said, and would twist people's words around to draw them into circular arguments.

"It's subtle so you kind of get sucked into it before you know where it's going,” the mother said of her boyfriend's habit of constantly picking at people's weak spots.

"He wouldn't call people names, it was more insidious than that,” she said. "I would define it as mentally or emotionally abusive.”

"He was always at the house, he made us feel like intruders,” the girl's brother said of the man . "He just sat around drinking beer all day.

"... He wasn't wanted there.”

But even her brother, who knew his little sister was depressed and hated the man they lived with, didn't believe his ears when the girl called him that morning and told him what she'd done. He told the court he figured she was hallucinating.

She was not. She had stabbed the man 11 times in the back and chest.

One of the knife thrusts went through his ribs and punctured a lung. He died on the floor in front of his chair, as the girl's mother, brother and a team of paramedics attempted to save him.

The girl turned herself in to police and told them she didn't really know what had happened.

After a week-long trial, held in December 2010, no one was any the wiser.

As Judge John Faulkner said today: "It is like reading a book with the final chapter missing.”

As the girl told police, a court-ordered psychiatrist and the judge, she couldn't remember actually stabbing the man.

She remembered him coming into the small kitchen where she was getting herself a glass of juice and feeling angry that he was invading her personal space, her "bubble” as she put it, then nothing.

"Him coming into the kitchen just crossed a line, I think,” she told the court when she took the stand during the trial. "... I just recall the turning around motion ... I don't recall getting or selecting a knife or hitting him.

"... The only thing I can recall (after that) is a picture ... of him on top of me. Not lying down, but like falling on me.”

The girl never denied stabbing the man, and pleaded guilty to manslaughter, claiming she did not mean to kill him.

The psychiatrist who assessed her after the fact told the court he believed she went into a "dissociative state” and was therefore not responsible for her actions.

"She went into a rage – and out of rage, she acted against the victim,” Dr. Kulwant Riar told the court.

Her rage was not the normal anger experienced by people all the time, he said, but a temporary disassociated state, meaning she had no awareness of her actions.

"That's how rage operates,” he said. "The person does not know what they are doing.”

In handing down his decision on the case today, Faulkner said he was not convinced by Riar's expert opinion because "there was no evidence of mental disorder or any previous psychotic event.”

But in the end, it was the unanswered questions which left the judge unable to convict the girl of murder.

"Guilty of manslaughter,” he ruled.

The girl, who all through the trial remained calm and unemotional, started crying. Her mother and father, long separated but sitting close as they awaited the verdict, hugged one another.

Outside the courtroom, she promised her temporary guardian she would be back at school by the fourth period.

Five months after her arrest, she was released into the care of an ex-police officer, and permitted to return to school. Since then, she has gone from barely passing to being an honour role student.

During the trial, she told the judge she wants to become a nurse, and at her sentencing hearing, the court will hear she has been accepted to university.

No date has been set for her sentencing hearing, which will have to wait for another psychiatric assessment.

The girl's identity is protected under the Youth Criminal Justice Act, which seeks to rehabilitate and reintegrate young offenders into their communities without the stigma of a criminal history.