A Northern Territory policeman’s long-awaited trial for allegedly murdering an Aboriginal teenager during an outback arrest is to be postponed for a third time.

Constable Zachary Rolfe, 30, has pleaded not guilty to murdering Kumanjayi Walker, 19, in November 2019.

The teenager was shot three times in the remote community of Yuendumu, about 290km northwest of Alice Springs.

Constable Rolfe was scheduled to stand trial in the NT Supreme Court in Darwin at 10am (ACST) on Monday.

But an hour before the proceedings were due to start, the High Court granted the prosecution’s application for a stay order.

Justice Jacqueline Gleeson granted the stay until September 10, when an application for special leave to the High Court will be heard.

The prosecution seeks to appeal a recent legal decision by a full bench of the NT Supreme Court related to Constable Rolfe’s defence.

Prosecutor Philip Strickland SC said the decision to allow Constable Rolfe’s legal team to use three separate defences before the jury, including the immunity clause in the NT Police Administration Act, was wrong.

He said it was not consistent with the criminal code, which required a police officer’s actions to be reasonable for immunity to apply.

He said the criminal code’s reasonableness provision was designed to protect the public from the excessive use of force.

The interpretation of the act is central to Constable Rolfe’s trial.

Justice Gleeson noted it was a “matter of significant public importance, and that the Crown had substantial prospects of obtaining a grant of special leave to appeal, and that there were exceptional circumstances warranting a stay pending the determination of the application”.

Constable Rolfe is charged with murder and the alternative counts of manslaughter and engaging in a violent act causing death.

His trial has previously been postponed twice by the COVID-19 pandemic.

When the trial goes ahead at a date yet to be fixed, it is expected to run for three weeks with about 50 witnesses and experts.

Darwin is about 1500 kilometres north of Yuendumu.

-AAP