WARNING: This story contains graphic details of violence.

Despite being mired in conspiracy theories and in the midst of psychosis, an Edmonton man knew what he was doing when killed a seven-year-old girl, an Edmonton judge ruled Friday.

Court of King's Bench Justice Steven Mandziuk convicted David Moss of second-degree murder in the death of Bella Rose Desrosiers on Friday.

"This was an unspeakable tragedy," Mandziuk said. "Mr. Moss took a young child's life in a shocking and agonizing way that has caused unimaginable damage to Bella's family, friends and community."

Moss, 37, didn't dispute that he killed the little girl, but he had sought to be found not criminally responsible, arguing he was suffering from a mental disorder and wasn't aware what he was doing was wrong.

After considering competing expert medical opinions about Moss's state at the time of the attack, Mandziuk rejected the defence's argument that Moss had developed schizophrenia-like psychosis as a result of a traumatic brain injury in 2004.

Instead, he accepted the evidence of medical experts, including those who had treated Moss in the wake of the attack, who opined that the psychosis was due to cannabis use, withdrawal or intoxication.

This finding negated Moss's ability to be found not criminally responsible, but the judge found that even if Moss had proved he was suffering from a mental disorder, he still wouldn't have accepted that he didn't understand the consequences of what he was doing.

"Being psychotic does not, in and of itself, negate intent. A person does not have to possess a clear and cogent understanding of reality to commit murder," he said.

Court heard that Moss, a tattoo artist, has struggled with anxiety, depression and sleep issues, and that he was engaged in various conspiracy theories. His beliefs intensified once the COVID-19 pandemic began.

'Delusional belief system'

During the trial, Moss testified that he was in an "illusion or screen world" when he killed Bella. Court heard he believed he was going through an "awakening" in the five days prior to the attack, and that he thought killing the girl would help her deceased father "ascend."

Following his arrest, he attempted suicide, attacked a nurse and continued to have symptoms of psychosis until about June 24, 2020.

Mandziuk found that while Moss had no reason to kill Bella Desrosiers "outside his delusional belief system," he was still aware of what he was doing and thus it does not negate his intent to commit murder.

A year before Bella's death, her mother Melissa Desrosiers became friends with Moss after getting a tattoo from him.

Two months later, Desrosiers' husband died by suicide in their south Edmonton home. Moss gave her a tattoo to commemorate her husband.

On May 18, 2020, Moss made comments that made Desrosiers believe he was suicidal, so she picked him up and brought him to her house.

She arranged with her aunt to come over to watch Bella and her then-four-year-old sister, while Moss went downstairs to shower.

The mother was tucking her children into bed in their bedroom when Moss appeared in the doorway in his underwear, holding a pair of kitchen scissors.

He pushed Desrosiers aside and slashed Bella's neck. Her mother tried to push him away from Bella, but was unsuccessful and was injured in the process.

Moss dragged Bella's body to the living room and continued to cut her with the scissors.

After the attack, he sat on the couch. Desrosiers grabbed the scissors and threw them outside. She called 911 and did First Aid on her daughter who had already died.

Members of both Moss and Bella's families sat in the courtroom gallery during the decision Friday.

In interviews following her daughter's death, Desrosier said Bella loved to play piano and sing, and that the seven-year-old was known in her neighbourhood for her lemonade stand where she raised money for Stollery Children's Hospital.

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