A police officer has been found guilty of assault and deprivation of liberty after pulling a gun on a couple for speeding along an outback Queensland highway.

A video recording that was tendered to court showed Senior Constable Stephen Flanagan swearing and honking as he tried to pull the couple over on the Landsborough Highway on the outskirts of Longreach in May last year.

As soon as the driver pulled off the road, the police officer — who has more than 25 years' experience — got out of his vehicle, pointing his gun and continuing to swear.

At a court hearing last month, Flanagan said he "feared for his life" after thinking the car was stolen and the driver was possibly armed.

In summarising, his lawyer Stephen Zillman said the video showed it was "clear he was very, very, highly stressed."

"It's not the case of some rogue lunatic police officer simply pulling pistols out, pulling them at someone who's been speeding," he said.

Senior Constable Flanagan will be sentenced in January. ( AAP: Dan Peled )

But prosecutor Jodie Wooldridge said at the hearing Flanagan could have used his radio or iPad to check if the car was stolen.

"The defendant's actions, in my submission, were to consciously escalate the situation, to use his weapon in a deliberately threatening way toward the complainant without any justification," she said.

Recordings also showed Flanagan handcuffing driver Lee Povey on the roadside.

Mr Povey claimed he also had a pistol pushed to his back — a claim that was disputed.

Magistrate Paul Kluck found Flanagan, who was stood down after being charged, guilty of assault and deprivation of liberty in the judge-only trial.

He did not accept evidence given by Flanagan, including that he thought his lights and sirens were working.

"This, in my opinion, has damaged his credibility irreparably," the magistrate said.

"I am not impressed by the defendant's evidence."