Dorian Barton, 32, an usher and part-time editor whose shoulder was broken on June 26, 2010, had ventured down to the Ontario legislature to scope out the scene.
A line of police officers in riot gear had formed to the south of him, and as he was facing east taking pictures of police horses he was hit from behind, Barton said.
"It was such a significant impact...I pretty much felt it all over," he testified. "I was knocked to the ground and I was stunned."
A witness, Andrew Wallace, said he saw Barton getting "charged" by a police officer, who hit Barton with his shield, knocking him over, and then struck Barton with his baton.
"It was disgusting," he testified. "A police officer who with no provocation...charged an unarmed person and attacked them."
Const. Glenn Weddell has pleaded not guilty to assault causing bodily harm and assault with a weapon. His lawyer, Peter Brauti, said at the start of the judge-alone trial that the only contact Weddell had with Barton was to help him up after he tripped.
Wallace was taking photographs of Barton's arrest and two videos of it also surfaced, yet none show Barton being knocked to the ground by a shield or being hit with a baton, Brauti noted.
"The video doesn't show everything that happened," Wallace said in the midst of a testy cross-examination by Brauti.
The clearest video starts with Barton already on the ground, one officer helps him up and quickly he is surrounded several other by officers in riot gear. They usher him a few steps forward then one of the officers appears to shove him and he trips over a curb and falls to the ground again.
The officer who pushed him, Brauti noted, quickly walks away and isn't seen on the video again.
After Barton's arrest Wallace took photos of the officer who he said had hit Barton and those photos were used to help identify Weddell.
The view of Barton on the ground for a second time is obscured by police officers and bystanders.
"There are no pictures in which you are seen being struck with a shield and there are no pictures of you being struck by a baton," Brauti said to Barton during his cross-examination.
One of the videos "suggests" he was hit with a baton after being knocked to the ground, Barton said, pointing out an officer who raises his baton just before the camera cuts away.
"It almost looks like I might be being hit there," Barton said of another point in the video. "It's hard to tell."
When Brauti said officers are trained to have their baton up and in a ready position while standing with their shields, Barton said he was unaware of that.
Barton admits his memory is "fuzzy," but he thinks he may have been hit with a baton or someone might have stepped on him. He was then dragged away by the police, which is clearly captured on the videos and in the photographs.
He had a broken shoulder, as well as bruises and scrapes, but can't say for sure what caused it. Brauti noted that when Barton fell, it looked like his arm was extended straight.
Barton was charged with obstructing a police officer and unlawful demonstration, though the charges were dropped soon after.
He talked to the Special Investigations Unit, an arm's-length agency that investigates certain allegations against police, the day after his arrest, but the case was closed and re-opened twice after none of the civilian or police witnesses could identify the "subject officer."
Barton also launched a civil lawsuit, but that was settled last year under terms that can't be disclosed.
The trial may wrap up as early as Tuesday.
Const. Babak Andalib-Goortani, the other officer facing charges stemming from the G20, is set to go to trial next week on two counts of assault with a weapon.
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