A mother found not guilty of attempted murder of her two sons due to mental incompetence has been ordered by a court to remain under mental health supervision for more than a decade.
Megan Somerville, 38, faced the South Australian Supreme Court on Tuesday to determine a period of supervision after she was in March found not guilty of attempted murder of her two sons due to mental incompetence caused by drug abuse.
The court had heard in August 2022 Somerville, from Modbury Heights in Adelaide’s north, stabbed her sons — then aged 3 and 8 — believing the boys were aliens out to kill her.
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The court was told she had pulled over her car while driving on the North-South Motorway at Wingfield to attack her children.
She was detained by a member of the public before emergency services arrived.
The court heard Somerville had been experiencing an “episode of psychosis” and had used both methamphetamine and cannabis in the hours before the stabbing.
One of the fathers of her children told the court he had found Somerville stashing “knives in the bedroom, under the pillows, inside clothing cupboards, under the bed and other hidden spots” before the attack.
The court on Tuesday ordered Somerville spend a limited term of 15 years under mental health supervision.
She has been under supervision since her arrest, and so the term has been reduced now to 12 years.
The court-ordered period under mental health supervision, in a secure facility or the community, is equal to the prison term a mentally competent person might receive for such a crime.

Previously Somerville had requested to be allowed from James Nash House, where she is being supervised, for weekly shopping trips, however, has since changed her mind.
On Tuesday she admitted to the court that she is not ready to be released into the community under any circumstances.
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