Prosecutors disagree, however, telling a jury on Tuesday that the accused did not need to knife the deceased even once.

Daniel James Sharpe is on trial in the NSW Supreme Court at Queanbeyan, having pleaded not guilty to a charge that he murdered 29-year-old Andrew Drake.

In her opening address, Crown prosecutor Kate Ratcliffe told jurors that Mr Drake had only just moved back to the family home in Surfside, just north of Batemans Bay, when he was killed.

She said that on the night of April 13, 2019, Mr Drake had dinner with his family before he and his sister Penny climbed over the back fence and onto the property of Mr Sharpe and his father David.

Ms Ratcliffe said the siblings had liked the sound of music coming from the Sharpe home, so they introduced themselves and were invited into a shed for drinks.

At one stage, the prosecutor said, David Sharpe "chastised" his son for breaking a glass and the younger Sharpe, embarrassed by this, went outside to have a "deep and meaningful" discussion with Ms Drake.

Ms Ratcliffe told the jury that the pair heard raised voices coming from inside the shed, so they went back in to find Mr Drake and David Sharpe "pushing and shoving".

She said Ms Drake "inserted herself in the tussle" and tried to push them apart, but at some point the woman received a blow to the face and her memory of what happened afterwards was "blurry".

David Sharpe, meanwhile, told police the entire incident was "a big blur".

Ms Ratcliffe said it was the Crown case, however, that Daniel Sharpe intervened in the fight between his father and Mr Drake, intentionally stabbing Mr Drake with a knife and accidentally slicing his father's hand in the process.

She said the younger Sharpe left Mr Drake dead with a total of 11 stab wounds, including one that passed through the 29-year-old's heart.

Ms Ratcliffe told the jury that while Daniel Sharpe would argue he had been defending his father, Mr Drake had not been armed and there had been no reason for Daniel Sharpe to stab him at all.

"There is no reasonable possibility that [Daniel Sharpe] believed it was necessary to do what he did," she said.

But defence barrister Troy Anderson said he would argue that Daniel Sharpe's actions had been "a reasonable response to the circumstances as [the accused] perceived them at the time".

He said his client's version was that Mr Drake had indeed been armed with a knife and that it was actually the 29-year-old who had slashed David Sharpe's hand.

This, Mr Anderson said, had led Daniel Sharpe to act "to defend his father from an ongoing attack".

He said there had been "no animosity" between the Sharpes and the Drakes, who "barely knew each other", before the incident.

"There was no reason for the accused to want to stab and kill the deceased, other than ... to defend his father," Mr Anderson told jurors.

The trial, which is expected to take a number of weeks, continues before Justice Geoffrey Bellew.