Senior Constable Ross Fowler was found guilty in March of recklessly causing injury to Brian Jackson during an arrest in February 2016.

The 51-year-old was called to a domestic dispute where he and a colleague attempted to arrest Mr Jackson at Frankston.

"Once arrested and handcuffed, whether because of frustration or anger, you gratuitously kicked Mr Jackson in the lower back as he was walking in front of you," Victorian County Court Judge Trevor Wraight said on Friday.

"Your kick was an entirely unnecessary act."

Before Mr Jackson was kicked in the back he'd been capsicum sprayed, kicked in the chest and was in handcuffs.

The judge also found it was "completely understandable" that the jury found his conduct to be illegal.

"It is difficult to see how you maintained your defence that somehow, your conduct of kicking Mr Jackson in the back while handcuffed, was justified and in the execution of your duty," he said.

Mr Jackson was left with some injuries after the attack but the greater impact on him was the psychological issues it caused, the judge said.

The prolonged court process had also left him drained.

The other officer, Senior Constable Travis Woolnough, was also charged over the arrest and was acquitted by the jury.

He has been returned to "gazetted duties", a Victoria Police spokesman confirmed.

Judge Wraight said the assault of Mr Jackson was of a "low level" and the senior constable lived an "honourable life and had an exemplary career" before this incident.

The judge also acknowledged Mr Jackson's conduct was frustrating for the officers, but found the victim was vulnerable when he was kicked.

Sen Const Fowler remained suspended from duty with pay and no further comment would be made, police said.

He was fined $10,000 but no conviction was recorded.

Australian Associated Press