Stabbed cousins saw SA accused hit woman

A young man accused of stabbing three cousins, murdering one, had earlier hit his partner in an argument on the street, a court has heard.

Daryl John Wise, 22, has gone on trial charged with the murder of 23-year-old Warren Treloar in Adelaide on December 7, 2013.

He is also charged with intentionally causing harm to the two other men.

In his opening on Monday, prosecutor Tim Preston said at least one of the cousins saw the accused hit his partner before all three intervened, with Wise getting punched in the face.

That scuffle ended and the cousins walked away, but Wise returned to his home to get a steak knife before coming after the group, the court heard.

"The accused pulled out the knife he had with him and swung it," Mr Preston told the South Australian Supreme Court.

Wise then went to flee but was chased, the court heard.

"The accused then turned and stabbed the deceased twice - once to the face and once to the chest, penetrating his heart," Mr Preston said.

Mr Treloar was dead before police and ambulance services arrived.

An autopsy showed he had alcohol, methylamphetamine and cannabis in his system.

Wise, who has a young child with his partner, turned himself in to police later the same day after disposing of the knife.

Mr Preston said the critical issue of the case will be whether or not Wise had acted in self defence.

The trial continues.