A court has heard Megan Somerville stabbed her children to ‘save them from a fate worse than death’

A mother accused of trying to murder her children said she was trying to ‘save them from a fate worse than death’ when she stabbed them on the side of a highway, a court has heard.

A mother accused of trying to murder her two children on the side of a busy motorway stabbed them to “save them from a fate worse than death”, and told first responders she was “proud of what I did”, a court has heard.

In CCTV and body worn footage played to the South Australian Supreme Court on Tuesday, Megan Jayne Somerville was allegedly filmed stabbing her two young sons on the side of the North South Motorway on the evening of August 15, 2022.

The court was shown four videos from the evening of Ms Somerville’s alleged attack, which her defence lawyer Jeff Powell said was fuelled by her underlying schizophrenia diagnosis rather than side effects from the illicit substances she took the day before.

The first clip showed footage of who prosecutors allege is Ms Somerville on the North South Motorway at about 11.25pm, seemingly stabbing her two children after pulling them from the car.

In the second, a concerned passer-by stops his vehicle and runs to the aid of the children.

Megan Jayne Somerville, 37, of Modbury Heights, is accused of stabbing her two sons in the middle of traffic on the North-South Motorway in August 2022. Picture: Facebook

She has pleaded not guilty by way of mental impairment. Picture: Facebook

The following footage played to the court showed body worn footage of the first SA Police officer on scene, and depicts Ms Somerville lying face down on the road after being detained by civilian witnesses.

The police officer asks her what happened to her children, to which she responded “I love my kids”.

“I’m proud of what I did,” she tells the officer.

Giving evidence to Justice Sandi McDonald, Dr William Brereton, a forensic psychiatrist at James Nash House who assessed Ms Somerville in September last year, told the court Ms Somerville’s recount of the incident included her fear that she and her children were “facing a fate worse than death”.

“She had such severe delusions that were of a certain nature that meant she thought her children were in danger of a fate worse than death, that they were being groomed to kill her, and that when that was done, they would be abducted, tortured and killed,” Dr Brereton said.

“And so, in harming the children she thought she was doing the right thing in the circumstances.”

Earlier in the week, the court heard Ms Somerville had returned positive blood test results for methylamphetamine and cannabis after she was assessed following the incident.

A concerned passer-by stopped his vehicle, coming to the aid of the children. Picture: 7NEWS

The court heard she had stabbed her kids to save them from “a fate worse than death”. Picture: Facebook

She has since pleaded not guilty to two charges of attempted murder by way of mental incompetence.

However, in South Australian law, a defence of mental impairment is not available to people who act under “self induced intoxication” – including those under the influence of illicit drugs – unless the presiding judge rules otherwise.

Mr Brereton said that, according to a witness affidavit filed on the prosecution case, Ms Somerville had been experiencing symptoms of psychosis on the days leading up to the incident, but had not ingested methylamphetamine until the day before.

He said that, taking into account her behaviours before the incident, it was likely that her mental condition had caused her to act, rather than the drugs.

He did however say that the quantity of meth and cannabis combined would have “severely exaggerated” Ms Somerville’s symptoms.

“The drugs were a substantial cause of the mental impairment,” Dr Brereton said.

“If the methylamphetamine and cannabis were a substantial cause of her psychosis, then my understanding is that she can have a mental impairment offence available to her, but Her Honour then has discretion on whether or not to (allow the defence).”

Ms Somerville will return to court on Friday.