TORONTO - Dorian Barton was taking a picture of a police horse during the G20 summit when he was slammed to the ground by riot police and "viciously assaulted" by six officers who broke his shoulder, he alleges.

Barton, 29, had never been to a protest before in his life, but went to the designated protest area at the Ontario legislature on June 26, 2010 to see the activity for himself.

He had been there only half an hour when he was knocked to the ground by a Toronto police officer with a riot shield, Barton alleges in a $250,000 lawsuit filed against the Toronto Police Services Board and seven unnamed officers.

"The conduct of the officers...was high-handed, criminal, wanton and callous and should attract the censure of the court," Barton's lawyer Clayton Ruby writes in the statement of claim.

None of the allegations have been proven in court. The Toronto Police Services Board has not yet filed a statement of defence, said another lawyer on the case.

The province's Special Investigations Unit already concluded a probe into Barton's complaint. Barton himself couldn't identify the officers, but neither could four witness police officers or two civilian witnesses.

"It is unclear how the complainant received his injury or who caused them," SIU director Ian Scott said in a news release in November.

"Accordingly, I cannot form reasonable grounds that a criminal offence occurred in the circumstances of this case."

A man who took photos of Barton's arrest came forward to the Toronto Star, and the face of at least one of the officers is clearly visible in the pictures. The SIU has been made aware of photos, said spokesman Frank Phillips, though he couldn't confirm if the photos have been given to the SIU.

"The director will be reviewing any new information that is forthcoming and at that time he'll make a decision whether the case will in fact be opened or remain closed," he said.

Earlier in the day on June 26 a small group of violent protesters rampaged through downtown Toronto, breaking windows and setting fire to abandoned police cruisers. The legislature protest was completely peaceful, Barton alleges.

"Despite this, at approximately 5 p.m. without any warning, riot police moved in on the peaceful protesters there," he says in the statement of claim.

"The police made no request or demand to the protesters to disperse. Riot police on foot pushed people back violently and targeted random persons for arrest."

Barton alleges he was one of those random people, and after being knocked to the ground, several officers assaulted him, hitting him in the face and stepping on his hands and feet.

Officers took him to the temporary detention centre and laughed when he complained about severe pain in his shoulder, Barton alleges.

"Dorian waited for five hours in extreme pain in a crowded cell before being sent to an on-site medic," he alleges in the statement of claim.

Barton was treated for a broken shoulder -- but handcuffed to the hospital bed -- and given only three regular Tylenols for his extreme pain, he alleges.

He was sent back to the detention centre after six hours and the next day was formally charged in court with obstructing a police officer and unlawful demonstration and was released on $1,000 bail.

Barton alleges six officers "viciously assaulted" him, and that the seventh, the one who charged him, "knew there was no basis to charge Dorian and did so knowing Dorian was innocent."

The Crown withdrew the charges against Barton at his subsequent court appearance on Aug. 23, when dozens of others also saw their G20-related charges withdrawn.