TORONTO -- An Ontario judge has cleared a man on a drunk driving charge after finding that he was assaulted by a Toronto police officer while waiting to take a breathalyzer test after his arrest.

In a decision released earlier this month, Ontario Court Judge Joseph Bovard says the assault on Jong-Won Jung constituted a "very serious breach" of his rights and as a result, the test results cannot be admitted as evidence.

Bovard also said he could not believe the testimony of the two officers who carried out the arrest, calling it vague and evasive and suggesting they were "not forthright with the court."

He further noted that one of the officers, Const. Amanpreet Gill, "demonstrated a belligerent and demeaning attitude" towards Jung at times -- for example, telling him to urinate in the back seat of the police cruiser when he expressed an urgent need for a bathroom.

Jung was arrested last year after he failed a late-night roadside breath test and both he and his girlfriend were taken to the police station.

The court decision says Jung took a first breath test at the station and was struck by Gill while waiting, handcuffed to a bench, to take a second test.

Jung's girlfriend had become agitated in the lobby and Gill was urging him to talk to her on a landline phone that was in the room, but Jung refused, saying he wanted to speak to a lawyer again instead, the document reads.

Jung testified that Gill grabbed him by the collar and shook him so aggressively that his head repeatedly hit the wall and the phone receiver, it says.

The incident ended when the other, more junior, officer, Const. Corey Sinclair, returned to the room and though Jung later alluded to it in front of Sinclair and another officer, no one looked into what happened, it says. No head injury was visible but he did develop a large bruise on his collarbone, the document says.

Gill, meanwhile, testified that he accidentally hit Jung with the receiver after the man pushed his hand away, but Bovard found his account unreliable.

"Officer Gill's evidence about the incident and about what happened afterwards was vague and at times evasive," he wrote.

"He said that he spoke to Mr. Jung about it afterwards and he checked for injuries. He thought that Mr. Jung mentioned injuries, but he could not remember if it was right after the incident or later, during the release procedure. He could not remember what Mr. Jung said about injuries. Officer Gill did not make any notes about the incident or about what happened afterwards," he said.

"I find this difficult to understand. This was an important episode; one about which an officer would be expected to make notes. This shows a lack of diligence with regard to the incident and perhaps an effort to obfuscate it."

What is clear, however, is that Jung's version of events was "completely plausible" and supported by the injury on his collarbone, the judge said.

"An assault on a person in custody while handcuffed to a bench to try to persuade him to do something that he has no obligation to do is indeed a grievous breach of the person's rights," he said.

"I find that the conduct of the police further exacerbates the breach," he said, noting their irregular testimony and the complete lack of followup or investigation after Jung indicated he had been assaulted.

"I find that in light of this very serious breach of Mr. Jung's right to security of the person, and considering the behaviour of the police regarding the breach, to admit the breath tests into evidence would bring the administration of justice into disrepute."