Patrick Allen Boon appeared via video link in the NSW Supreme Court in Sydney, where he admitted to the charge of killing his colleague, after the violent confrontation almost two years ago near Wee Waa.

In front of Justice Elizabeth Fullerton, Boon pleaded guilty to one charge on the indictment that he "on 14 June 2017, at Narrabri in the state of New South Wales, did murder Fred Tuff".

Justice Fullerton fixed a sentence hearing date at the end of next month.

It is expected to span much of the day as the defence and Crown tender evidence, including the police case, specialist reports, and submissions on any mitigating or aggravating factors that should be taken into account in the sentence.

READ ALSO:

Boon made no application for bail during the appearance and it was formally refused by Justice Fullerton.

Boon faces a maximum of life behind bars for the murder but is expected to be given a discount for his early guilty plea, which was entered before any trial date had been set.

The case had previously been adjourned several times to allow the Crown and defence to determine a location and length for the murder trial.

Boon attacked Mr Tuff, 57, with a wrench and a sledgehammer at the worksite off Culgoora Road at Wee Waa.

Boon was initially charged with wounding with intent to murder, but his charges were upgraded to murder a day later, after Mr Tuff died in hospital from massive head injuries.

Boon and Mr Tuff, both concreting contractors, had been working on the new $41 million Cotton Seed Distributors development.

The pair had both been contracted to work for Queensland-based company Boodles Concreting at the building site, which was being operated by Richard Crookes Constructions.