Toronto police Const. Babak Andalib-Goortani has been found guilty of assault with a weapon in the G20 arrest of protester Adam Nobody three years ago.
Nobody was singled out for arrest at a demonstration on June 26, 2010, at the Ontario legislature during the economic summit of world leaders. He was tackled as he ran from police and struck repeatedly with a baton.
"A police officer is not entitled to use unlimited force to effect an arrest," Judge Louise Botham said in her ruling.
The Crown had argued that Const. Andalib-Goortani was overwhelmed by the chaos and "lashed out" at Nobody, hitting him with a baton after the man had been wrestled to the ground.
Botham, however, said Andalib-Goortani's explanation that he was responding to Nobody's resistance is "nothing more than an after-the-fact attempt to justify his blows."
"I accept that in a dynamic situation, arrests need to occur quickly and officers may well need to use force to ensure that happens," Botham said. "[But] even on the defendant's evidence, the resistance offered by Adam Nobody was minimal."
Botham also called it curious that Andalib-Goortani was wearing no name tag or badge number on his uniform that day.
Nobody applauded when the verdict was read in the courtroom and told reporters outside he was "elated" about the decision. He was also surprised.
"We live in a system we all know that cops get off all the time, so yes, I can honestly say that I was [surprised]," he said.
In May, another officer, Const. Glenn Weddell was found not guilty of assault stemming from the G20 protests, which resulted in hundreds of arrests.
Toronto Police Association president Mike McCormack told CBC News he is "distraught" and "crushed" by the decision.
"We're going to have counsel go over it [the verdict] and then if there are grounds for appeal, we'll be taking that avenue."
Andalib-Goortani left the courtroom without speaking to reporters.
He will be sentenced in November.
Nobody also has a civil case pending against Andalib-Goortani and other officers.
With files from The Canadian Press