The officer, Sergeant Brett Coutts, used the OC spray on the alcohol-affected man outside the Cabinet nightclub in the early hours of May 26 last year.

The man had a blood-alcohol content of 0.12 and the court has heard evidence that he was in close proximity to Sergeant Coutts, was physically imposing, belligerent, giving small indications of violence and had appeared to flinch at the officer.

That flinch was not apparent on CCTV vision of the incident.

The drunk man had also reportedly placed his bloodied hand on a woman's breast earlier in the night.

Sergeant Coutts's lawyer John Purnell said on Thursday it was unlikely the officer would have been able to take the drunk man down, given his size.

Instead, the officer used his OC spray and put the man in a headlock, before placing him in the back of a caged vehicle.

Sergeant Coutts was dismissed from ACT Policing in June this year for his use of force, following an official internal investigation.

But he fought his sacking through the Federal Court, arguing he was unfairly dismissed, and that the AFP's decision-making process was flawed.

The case has been heard this month and both Mr Purnell and representatives for the Australian Federal Police Assistant Commissioner Leanne Close gave their closing submissions to Justice John Griffiths.

Mr Purnell said the officer was denied procedural fairness and was subjected to apprehended bias by those investigating his alleged excessive use of force.

He said that, among other things, crucial evidence material was not available to the author of a report into the incident.

Those claims were denied by lawyers for the AFP, who say the decision-making process was sound. They argue that questions of partiality did not take into account the fact that an independent review was conducted of the findings against Sergeant Coutts.

They said there was no suggestion that the author of the independent review was not fair.

Justice Griffiths reserved his decision on Thursday afternoon.