As a murder trial ended in Rossland, B.C., both Crown and defence lawyers agreed that Kimberly Ruth Noyes was in a psychotic state when she killed a 12-year-old boy.

Her lawyer, Deanne Gaffar, told B.C. Supreme Court Justice Mark McEwan Wednesday that Noyes can't be held criminally responsible for the death of John Fulton on Aug. 13, 2009.

"This is a devastating and tragic case when a young man was killed by a person, who when not ill, is described as a gentle and kind person," Gaffar told the court.

A person found criminally responsible for committing an offence must "have an understanding of the act, not a mere knowledge of what is taking place," she said.

McEwan will give his verdict Friday in the second-degree murder case.

Earlier trial evidence heard that Noyes, 43, knew ahead of time that she was going to kill Fulton, but several psychiatrists testified she had no concept that her actions would be permanent and that she thought it was a dream.

The law states that if a person doesn't know right from wrong they should be excused from what otherwise would be criminal behaviour, Gaffar told the judge.

Crown prosecutor Phillip Seagram didn't argue with Gaffar's conclusions.

"Police evidence is significant because it noted her demeanour very close to the event, before and after," he said, referring to Noyes.

A video played during the trial showed Noyes being interviewed right after her arrest and it provided "some sense of her mind at the time of the murder," Seagram said.

A list of expert witnesses and testimony from Noyes' daughter and sisters all showed there was some history of mental illness, he said.

Evidence showed in 2002 Noyes was diagnosed with post-partum mania after the birth of her son and in 2009 she had violent encounters with her sister and brother-in-law.

"No or few unproven facts (are) left by experts at arriving at their conclusions," Seagram said.

"I have confidence in the experts as they had a high degree of confidence in their conclusions."

The trial heard in the weeks before the autistic boy was found stabbed to death in the woman's home that Noyes had stopped taking medication for her mental illness.

Noyes' family doctor and a psychiatrist both testified there were times when the Grand Forks, B.C., woman took herself off prescribed treatment against medical recommendation.

Fulton disappeared from the front steps of his neighbouring home last August and wasn't found until two days later, after a search of the area.