A teenager who was punched in the face twice by a police officer after being pulled over for not signalling a lane change had his rights repeatedly violated, an Ottawa judge has ruled.

Justice Julie Bourgeois found Mohamed Hamed not guilty of possession of marijuana, possession of counterfeit currency and resisting arrest, saying the evidence against him was inadmissible in light of the rights breaches.

In a decision released last week, Bourgeois said there was "no basis" for Hamed's arrest or for a search of his van, which was conducted without a warrant and led to the seizure of some 200 grams of marijuana.

The judge further said Const. Nikolas Boldirev used excessive force when he punched Hamed in the face twice at full force while the teen sat handcuffed in the back of a police cruiser.

She also said the fact the officer waited 11 minutes to inform Hamed of his right to a lawyer, and then failed to call one, suggests there is a "systemic problem" within the Ottawa force.

Bourgeois said the officer's testimony at trial lacked credibility and his reasoning for punching Hamed was "completely ridiculous."

"The two punches to Mr. Hamed's facial area were completely contrary to the principles of proportionality, necessity and reasonableness," she wrote.

"Mr. Hamed's hands were cuffed to the back. He was sitting on the back seat of the police cruiser with his legs and feet outside the car. He was completely vulnerable. Const. Boldirev was not in a vulnerable position. There was no emergency to the situation."

A spokesperson for Ottawa police said Tuesday that an internal investigation is underway as a result of the ruling and Boldirev has been assigned to administrative duties.

Bourgeois recounted the details of the case in her ruling, saying Hamed was pulled over just before 2 a.m. on Aug. 31, 2015, a stone's throw from his home. He was 19 at the time and had no criminal record.

The teen testified at trial that he had bought pot for an upcoming cottage trip with friends but hadn't opened the plastic bag it came in, though he had smoked part of a joint several hours earlier. A backpack containing the marijuana was stashed under the passenger seat, he said.

He also told the court that he had vacuumed the van he had been driving that morning and consistently used air fresheners in an effort to hide his pot smoking from his dad.

Hamed said he co-operated with the officer until he was ordered to step out of the van, at which point he asked to be told why. No explanation was given despite repeated requests, he said, and Boldirev unlocked and opened the door himself.

The teen said he kept asking for answers during a rough search and while being pushed into the cruiser. He testified that Boldirev slapped him on the back of the head, then delivered the punches after the teen complained.

Boldirev didn't ask if he needed medical attention and went on to search the van, the young man said.

Only afterward did the constable tell Hamed about his right to a lawyer, though one was never called during the incident, he said. The teen was released to his father a short time later.

Hamed told the court he was shocked and scared throughout the encounter, and felt he was being treated like a "hood rat."

Boldirev, meanwhile, testified that after checking Hamed's documents he smelled a "pungent" odour of fresh marijuana and saw a few flakes of marijuana on the floor and driver's seat of the otherwise spotless van.

The constable told the court he informed Hamed about his observations and instructed Hamed to get out of the van, then handcuffed the teen, took him to the cruiser and searched him, seizing two cellphones and a wallet.

Boldirev said that when he went to put Hamed in the cruiser, the teen began to resist by tensing his body and planting his feet. The officer said he managed to push Hamed into the cruiser, but the young man's legs were still outside.

He testified he punched Hamed in the face because the teen was trying to get up and escape 芒鈧珺次元官网网址� an argument the judge rejected, saying there was no evidence to support such a conclusion.

In fact, there was no reason to stop Hamed in the first place since his lane change didn't affect traffic or put anyone at risk, Bourgeois said in her ruling.

Nor did the judge believe Boldirev saw or smelled marijuana in the van, or that he told Hamed the reason for his arrest.

While police officers cannot be held to a standard of perfection, Bourgeois found that Boldirev's actions were "well below the standard expected of a police officer in similar circumstances."

Paola Loriggio, The Canadian Press