Intoxication will play a major part in the defence of two Irish tourists accused of murdering a 66-year-old Indigenous man in Sydney, a court has heard.

Nathan Kelly, 22, and Christopher McLaughlin, 25, are alleged to have murdered Paul William Tavelardis in the inner-western suburb of Summer Hill in December.

The men, reportedly from Co Donegal, had been charged with recklessly causing grievous bodily harm until Mr Tavelardis died in hospital in January and their charges were upgraded.

The pair appeared in the New South Wales Supreme Court on audio-visual link from a prison in Sydney's eastern suburbs, both wearing button-up prison-green polo shirts.

Neither entered a plea via their barrister, Margaret Cunneen.

Justice Elizabeth Fullerton told Ms Cunneen it was clear that "very, very severe intoxication by alcohol" was a factor in the alleged crime.

Ms Fullerton added that there was "some degree of incapacity" by the two men at the time of the incident.

Attempts at setting a trial date in March, May or June, 2020 failed as the prosecution and defence have yet to agree on key facts regarding intoxication.

The pair will next appear in the same court on 14 February 2020.