Daniel James Bluett was charged with two counts of common assault in relation to an incident that occurred about 3.40am at a CBD taxi rank on February 24 last year.

He became involved in an argument with a woman who he struck to the face, causing her to fall to the ground unconscious. The first assault charge was upheld in the Magistrates Court.

A second woman saw the incident and checked on the woman before shouting at Bluett. A taxi driver and another witness told police the woman attempted to strike Bluett but may have only grazed him, and Bluett then threw a "blind punch" which knocked her to the ground.

She suffered a broken jaw.

Bluett claimed a number of men and women were shouting at him after the initial assault, and he felt a punch to his eye so he swung his hand in a defensive motion but was unaware he had struck a woman.

Some evidence suggested Bluett may have struck the woman a second time, but Magistrate Ken Stanton excluded this and summarised that the punch on the second woman was in self-defence.

The second charge of assault was dismissed.

The Director of Public Prosecutions appealed this ruling in the Supreme Court.

Justice Michael Brett found the magistrate did not consider whether the use of force against the second woman was "reasonable in the circumstances".

"His Honour had found that the punch by the respondent was in response to a threatened or actual assault upon him by the second complainant," he said.

"However, a blow delivered in response to an earlier blow is not necessarily delivered in lawful self-defence.

"It will only be so if it is force which is reasonably necessary in the circumstances as the respondent believed them to be."

Justice Brett found it was unclear whether the magistrate had come to his conclusions based on the evidence of Bluett "in the circumstances as he believes them to be" - evidence which the magistrate found to be inconsistent.

In his ruling earlier this month, Justice Brett ruled that the matter return to the Magistrates Court for "better reasons" within 30 days.