An ACT Supreme Court jury has taken just 90 minutes to find a former police sergeant not guilty of inappropriately using capsicum spray on a Canberra woman.

David Fearnside sprayed Fiona Corrigan, 24, with capsicum foam when she was in a padded cell at the city watch-house in 2006.

She had been brought into the station after biting an officer.

The prosecution alleged Fearnside acted out of arrogance and to punish her.

But his defence counsel argued it was his duty to spray her to stop her from harming herself.

Outside the court, Mr Fearnside said he was disappointed at being charged for doing his duty.

He has called on the AFP Commissioner to publicly reinstate him as a sergeant.