On the first day of her trial for second degree murder, Christine Longridge pleaded not guilty – her lawyer argued she should not be held criminally responsible for her daughter’s death in Dec. 2016, because she suffers from mental illness.

Longridge was charged with second degree murder, and possession of an offensive weapon in the death of her 21-year-old daughter Rachael on December 23, 2016.

An agreed statement of facts outlined Longridge’s long history of mental illness – saying she was diagnosed with bipolar disorder after her son Michael was born in 1998, and the mother of two had been hospitalized four times, the last time in late November, a few weeks before her daughter’s death.

“She did it to fulfill what I would call the ‘messiah mission’,” defence lawyer Dino Bottos said in an interview with CTV News.

“In order to save her son Michael, who she thought was the messiah; she was compelled to kill Rachael, and then herself.”

The Medical Examiner found Rachael was nearly decapitated.

In court, the defence argued Longridge shouldn’t be held criminally responsible.

“She didn’t know what she was doing was morally wrong, because she was acting on the voice of a higher being,” Bottos said.

Two witnesses were called to testify by the defence Wednesday, Don Metz, a longtime family friend who described Longridge as a “loving, supportive mother”, and as someone who was “quiet, shy, but always seemed normal.”

“Nobody saw this coming,” Metz said.

Longridge’s sister said Rachael and Michael “were her world”, and “she did not know what she did that day.”

“She was not herself that night,” Bottos said.

After her diagnosis in 1999, the agreed statement of facts said her husband Erin Longridge played an important role in ensuring Longridge took her medications.

Her condition worsened when her husband died from throat cancer in 2015 – she started taking her medications less.

Longridge is being held at Alberta Hospital, she’s had two psychiatric assessments in the last year.

On Thursday and Friday, the defence is expected to bring in two forensic psychologists from Alberta Hospital to testify on Longridge’s mental health.

With files from Shanelle Kaul