Constable Zachary Rolfe stands charged with the murder of Kumanjayi Walker in the Central Australian remote community of Yuendumu in 2019. The 19-year-old died after he was shot three times.

Mr Rolfe, who is pleading not guilty, arrived at the Darwin Supreme Court on Monday morning for the first day of his trial after it was delayed a number of times because of COVID-19.

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The trial was initially set to run for three weeks, but presiding judge Justice John Burns told potential jurors the trial was now expected to last four weeks.

This is because jurors will sit for less than four hours a day - from 9.30am to 1.15pm, instead of the usual 4pm finish time - to reduce the chances of jurors contracting COVID or becoming a close contact and having to isolate.

A court spokesperson said, "Inside court, the jury will be divided to maximise the space between them, so they will not all be seated in the jury box as is usually the case."

Sitting for less than four hours a day will also help prevent jury members from being deemed close contacts and having to isolate if someone becomes infected.

The definition of a close contact changed nationally in late December to a person who has spent four hours or more with a confirmed case.

Jury empanelment was underway on Monday. Fourteen jurors are set to be chosen from the pool. A number of potential jurors have asked to be excused.

The opening addresses from the defence and the prosecution will commence following the jury empanelment.

The trial was first postponed in July when the Crown's interstate prosecution team was unable to travel to the NT from Sydney due to NT COVID-19 border restrictions.

The second postponement was in mid-August when parts of the Top End were locked down after a virus outbreak in Darwin.

The most recent delay in late August was due to a High Court challenge over Mr Rolfe's proposed defence.

A large contingent of media has converged on the court with pre-trial news stories appearing internationally, including in the Washington Post.

Mr Rolfe is charged with murder, with alternative counts of manslaughter and engaging in a violent act causing death. He has pleaded not guilty.

He is being defended by David Edwardson QC while Philip Strickland SC will prosecute for the Crown.

with AAP