Magistrate Michael Antrum found the former-NSW police officer Nigel Alfred Davey, 47, guilty in the Queanbeyan Local Court on Tuesday.

Mr Antrum found Davey had lied to a Nowra court on October 1, 2014 when he said Regan Sutton was armed with a knife and had tried to attack him before Davey Tasered him on June 14, 2013.

It was found Mr Sutton had told Davey "f--- you" before the then-police sergeant, still seated in his squad car, tasered an unarmed Mr Sutton from five metres away.

According to public posts on his Facebook page, Davey worked as a teacher in the ACT between February and December 2016.

The ACT Education Directorate could not confirm if it had employed Davey because of privacy considerations nor whether he had undergone a background check before or after his employment commenced.

In a reply to a friend on his Facebook page, Davey comments he was "to violent [sic]" to be a police officer.

The court also heard in 2014, that by the time of the hearing against Mr Sutton, Davey had been suspended by NSW Police because of an incident on Australia Day in 2014 that also involved a Taser.

The court was also told in 2014 Davey's fellow officers had complained he was "unstable", addicted to opiates, stole opiates from people he searched in the street and fabricated fact sheets. Davey denied all those allegations at the time.

NSW Police said Davey's employment was terminated in 2015. No internal action was taken against Davey regarding the incident with Mr Sutton because "the officer had already been removed for another reason".

The internal investigation was now with the NSW police watchdog, the Law Enforcement Conduct Commission.

Davey was on duty alone during the incident and a NSW police spokesperson said police in the Shoalhaven Local Area Command, which oversees Nowra, were still allowed to go out alone.

In June 2013, Davey stopped parallel to Mr Sutton on Nowra's McKay Street at about 10.20pm. He originally claimed an armed Mr Sutton had approached the car and tried to stab him.

Cross-examiniation by Mr Sutton's lawyer, Steven Boland, revealed Davey didn't remember seeing a knife on Mr Sutton but claimed the knife must have flown from his hand when he was tasered and landed behind a fence.

Davey also couldn't explain how Mr Sutton was five metres away when he'd been close enough to stab him.

Mr Sutton did have a knife earlier that evening, but had disposed of it before he was stopped. Mr Antrum said on Tuesday the distance was too great between the knife and where Mr Sutton was Tasered, concluding Mr Sutton was unarmed.

Court documents showed Davey discharged the Taser three times. Police body-cam footage of the incident tendered in court, which records automatically once a Taser is drawn, showed Mr Sutton incapacitated on the ground and screaming.

Mr Antrum said it was important Tasers weren't used to "terrorise merely unhelpful members of the community".

Even if Mr Sutton had been armed, Mr Antrum said reasonable alternatives, such as driving off, were available to Davey.

Davey, who fronted the court in a black suit, is to be sentenced early next year.

With Elliot Williams.