The Toronto police officer who orchestrated the mass arrest of over 1,000 peaceful demonstrators and bystanders during the 2010 G20 summit was found guilty on Tuesday of discreditable conduct and unnecessary exercise of authority.

"This decision to order mass arrests demonstrated a lack of understanding of the right to protest," retired Ontario Superior Court judge John Hamilton said of Supt. Mark Fenton as he handed down the ruling.

Over the course of the G20 summit weekend, which took place on June 26-27, 2010 in the Canadian province capital, approximately 1,100 were arrested and detained after a group of "Black bloc" demonstrators reportedly broke off from the peaceful rally and began smashing windows along Queen Street.

The Toronto Star reports:

The charges stemmed from Fenton’s orders to blockade protesters in so-called “kettles” twice. The first occurred on June 26, 2010, after a small group of protesters smashed windows and lit fire to police cars in the downtown core. Fenton ordered officers to “kettle,” or box in, protesters in front of the Novotel hotel on the Esplanade, and more than 260 people were arrested and taken to a makeshift prisoner processing centre. The next day, just moments after coming on shift, the upper command officer ordered police to box in hundreds of people at the intersection of Queen St. W. and Spadina Ave. during a thunderstorm.

According to various accounts, including one by Canadian author and activist Naomi Klein, demonstrators were attacked by police batons and pepper sprayed before roughly 800 were thrown in jail, where they faced a host of other abuses. The crackdown marked the largest mass arrest in Canada's peacetime history.

Most of the demonstrators were never charged.

Fenton, who is the only senior official to face a police tribunal over the incident, was found guilty of three of the five charges against him and will be sentenced in December. He faces a possible reprimand or dismissal.