Megan Jayne Somerville on both illicit and prescription drugs when she stabbed her children, court told

A mother who said she was not guilty of stabbing her children on the side of a highway was on drugs during the incident, a court has heard.

A mother charged with the attempted murder of her two children after allegedly stabbing them on the side of a busy Adelaide motorway was under the effects of meth, cannabis and prescription medication on the night of the incident, a court has heard.

In the Supreme Court on Monday morning, Megan Jayne Somerville appeared via video link from a closed mental health facility where she has been since her arrest in August 2022.

In December 2022, Ms Somerville, 37, pleaded not guilty to two charges of attempted murder by way of mental incompetence.

The charges arise from an incident on August 15, 2022, when police were called to the North-South Motorway just before 11:30pm following reports a woman had been detained by a member of the public.

The court previously heard Ms Somerville, of Modbury Heights, stopped her silver Honda sedan and removed her two sons, aged 3 and 8 at the time, before stabbing them “a number of times” with a knife.

Megan Jayne Somerville pleaded not guilty to attempted murder by way of mental incompetence. Picture: Facebook

The court heard she was on drugs at the time of the alleged incident. Picture: Facebook

In October last year, Justice Sandi McDonald heard Ms Somerville would likely not be contesting the elements of the crime – that she did stab her two children – but reports prepared by the defence concluded that Ms Somerville was mentally incompetent at the time of the attack.

The court on Monday however heard Ms Somerville, who is understood to have a history of mental illness and drug addiction, had been a “frequent” drug user, with a significant amount of both illicit and prescription drugs found in her blood after the incident.

Giving evidence on her drug use to the court, Professor Jason White told the court that the levels of methamphetamine and cannabis found in her system matched that of a “frequent” or “daily drug user”.

He said Ms Somerville had two lots of blood taken after emergency services arrived on the scene – the first at about 12.50am, 85 minutes after the alleged incident, and the second about 14 hours after the first test.

“Methylamphetamine was detected in the blood sample, which is illicit in Australia. Amphetamine was also detected, that is both a therapeutic and an illicit drug,” he said.

“THC was also detected, which is the main active compound in cannabis.”

Professor White said that at the time of her first test, Ms Somerville returned a positive methylamphetamine result of 0.39mg per litre of blood, which means at the time of the incident, it would have been as high as 0.43mg.

She will return to court later this week. Picture: Facebook

“Therapeutic concentrations (of the drug) typically are in the range of .02 to .05, so (her results) were about ten times that,” he said.

That amount of the drug, professor White said, would likely make the user impulsive, confused, agitated, paranoid and obsessive.

He told prosecutor Lucy Boord SC that any side effects of meth could be exaggerated by an underlying condition, such as schizophrenia.

He said two of Ms Somerville’s prescribed antipsychotic medications were also detected in the blood tests.

The court heard a friend of Ms Somerville had given evidence that the mother of two had “obtained” an “8-ball” of meth the night before she allegedly stabbed her children.

Justice McDonald will hear further evidence later this week.

Originally published as Megan Jayne Somerville on both illicit and prescription drugs when she stabbed her children, court told