A jury's decision to find a man guilty of murder after he killed two people in a head-on collision is a South Australian first, the victims rights' commissioner says.

Whyalla man Michael Frank Knowles, 38, deliberately drove his vehicle into an oncoming car killing Natasha Turnbull and James Stephen Moore, both 24, in December 2014.

During the trial in the Port Augusta Supreme Court, the jury was told Knowles was suicidal and had often spoke of killing himself by crashing into an oncoming vehicle.

He was yesterday found guilty of murder, and is due to be sentenced this morning.

Victims rights' commissioner Michael O'Connell said the jury's decision was a landmark case for South Australia.

"The jury's decision is quite profound," he said.

"It's a landmark [decision] to the extent that to the best of my memory in modern history in this state, a driver of a motor vehicle that has killed other people has managed to avoid being prosecuted and found guilty of murder.

"This is an important statement and it's a statement that shows that the harm that is being done to victims, when the evidence is there, can be acknowledged."

Mr O'Connell said the verdict could give police confidence to charge drivers involved in future fatal road crashes with murder, if circumstances were appropriate.

"What it suggests now is if there is evidence that is strong enough that there is an alternative, that there is a willingness to prosecute for more serious offences," Mr O'Connell said.

"For some period of time, dangerous driving or culpable negligent driving has been looked upon as the most serious driving offence on a road way.

"Quite clearly now there is a preparedness to prosecute for murder, where the evidence is there and let the jury determine whether guilt is proven or not."