The sentencing judge also said the now former officer had exploited the victim's submission to authority and later minimised his criminal conduct in a police report.

A jury found Wade Joseph Howell, 36, guilty last month of intentionally or recklessly inflicting actual bodily harm after he bashed the victim in Veterans Park early on April 2, 2016.

Howell, who was in Canberra for police training on close personal protection, was out drinking at Civic nightspot Mooseheads when he followed a woman heading back to her hotel at the Medina Apartments.

The off-duty police officer from Melbourne was sitting on a park bench with the woman when her boyfriend came hurrying up to them.

The woman warned her boyfriend not to hit Howell because he was an officer.

The trial heard Howell pushed the man away, to which the man replied: "What the f--k?"

Howell then punched him in the head several times.

When the man fell to the ground, Howell continued to land blows on the man's head.

The jury rejected Howell's claim that his actions were justified by self-defence.

The victim in the assault suffered a broken cheekbone and a swollen face, as well as ongoing nerve damage that caused numbness and a lost sense of taste.

After the assault Howell followed the victim back to the apartment, where Howell called police, and where he tried to persuade the woman that she did not want her boyfriend to stay that night.

Howell was found guilty of the assault, but was acquitted of a separate charge of choking, and a charge of perverting the course of justice by his actions later that night.

The former police officer appeared in the ACT Supreme Court on Friday to be sentenced.

During the sentence, Justice David Mossop said Howell's actions after the bashing were relevant to his level of remorse.

He said Howell had gone back to the couple's apartment and tried to persuade the woman she did not want the victim to stay that night.

He had tried to direct the authorities' attention away from what had happened.

Howell had exploited the victim's submissiveness to authority, and tried to falsely downplay his own actions, the judge said.

The former officer had also minimised his criminal conduct in a later police report, he said.

There was a complete absence of remorse or contrition for the harm he had caused, the judge said.

And false versions of the assault had been put to the witnesses during the trial.

But the judge commended the two police officers who had seen what had happened in the fall out of that night and ensured the assault was reported.

The court heard Howell had since left his job with the federal police.

He had been first suspended with partial pay, then suspended without pay, and then during his trial was given notice to show cause why he should continue in the job.

Howell resigned, and was now working as a driver, the court heard.

His barrister said the loss of his "cherished" career was already a significant penalty.

The court also heard Howell had no criminal history.

Justice Mossop noted the assault had had "catastrophic" consequences on Howell's career.

There were multiple accounts before the court that he had been a dedicated and competent police officer.

The assault was out of character, the court heard, and Howell was not usually an aggressive man when drinking.

The judge sentenced Howell to six months jail but suspended the whole sentence.

He put the former police officer on a good behaviour order for 30 months.