A WOMAN “erupted” and stabbed her estranged husband in the neck, in front of their sleeping son, because he would not return to their sexually “tumultuous” marriage, a court has heard.

A Supreme Court jury has been told the violent altercation ended a complex relationship between the pair that included multiple partners and “sex parties” in the Adelaide Hills.

Jurors were told that, after trysts with another woman and a man, the wife tried to restart her marriage — and fell pregnant to her husband during a threesome on her birthday.

Carmen Matteo, prosecuting, said the incident had the hallmarks of a crime of passion.

“I want to be very clear that this is not a case in which we allege a cold, calculated, pre-planned attempt on the husband’s life, not at all,” she said.

“We say that the behaviour of the wife was more like an eruption of long-held frustrations and emotions toward her husband and the state of her marriage.

“She held murderous intent at the time of the stabbing.”

The wife, whose identity is suppressed, has pleaded not guilty to one count of attempted murder and one count of causing serious harm with intent to do so.

The offences allegedly occurred at the home the estranged couple shared with their son, in the northern suburbs, in March last year.

The husband was rushed to hospital with a life-threatening puncture to his jugular vein and would have died if not for immediate surgery.

Opening the trial, Ms Matteo said the couple’s relationship prior to the incident was “tumultuous to say the least”.

“It involved marital separation, shared custody of their five-year-old son and a degree of to-ing and fro-ing about whether they would get back together,” she said.

“Theirs was a complex relationship which might explain why, at the moment of stabbing her husband, the wife was motivated to such extreme action.”

Ms Matteo said the wife had extramarital relationships with another woman and a man while continuing to live with her husband.

She said he agreed to stay in the house and help care for their son, but the couple continued to have “on-and-off” sex with one another.

However, when the husband began an extramarital relationship of his own, the wife reacted violently, punching him in the face, placing him in headlocks and trying to take his phone.

Ms Matteo said that, by February 2014, the wife once again wanted an exclusive relationship with her husband, but he wanted to stay with his new partner.

“On one occasion, the wife turned up at the house with a card (saying) ‘Stalker is such a harsh word, I prefer Valentine’,” she said.

“She would send 35 text messages (a day) and call him more than 20 times.

“One message read ‘my shoes can never be filled, if another chick thought she could take my place it’s a big joke’.”

Ms Matteo said the issue came to a head while the couple’s son was sleeping and the wife stabbed the husband in the neck with a small paring knife.

She said the wife called 000 claiming to have acted in self-defence — but Ms Matteo insisted the wife’s intent was to murder her husband.

David Moen, for the wife, asked jurors to carefully consider the evidence as it unfolded — including the fact the husband’s DNA had been found on the handle of the knife.

He said his client suffered injuries to her chest and body during the incident, and was 10 weeks pregnant with the couple’s second child at that time.

Mr Moen said that child was unexpectedly conceived during a threesome between the couple and another woman, which had been planned to celebrate the wife’s birthday.

He said that sexual encounter followed on from her request, to her husband, that they stop attending “sex parties in the Adelaide Hills”.

The trial, before Justice John Sulan, continues.