TORONTO - A young woman who pleaded guilty to wearing a disguise and mischief during the anti-G20 protests two years ago had a limited leadership role in the vandalism that plagued the Toronto summit, a judge ruled Monday.

In his decision, Ontario Superior Court Justice John McMahon accepted that Kelly Pflug-Back, of Guelph, Ont., at one point gave instructions to vandals dressed in black as they moved up Yonge Street smashing windows.

Pflug-Back, who is in her early 20s, pleaded guilty in February in Ontario Superior Court to several charges, including wearing a disguise and seven counts of mischief over $5,000.

At the pre-sentencing hearing, the Crown tried to prove she was one of the "directing minds" of the vandalism that erupted in the downtown, which would be considered as "an aggravating feature" in sentencing.

"Ms. Pflug-Back was more than just a sheep," prosecutor Liz Nadeau told court.

"She was definitely one of the leaders."

The Crown's lone witness, Det. Const. Andrew Hassall testified that Pflug-Back yelled "Hurry up!" as several of the so-called Black Bloc members smashed a Bell store window.

About four or five vandals, who were toward the front end of a large group of protesters, then stopped in front of a nearby perfume store.

"Leave it alone. We only want big business," Hassall quoted her as yelling.

"They spared it after Ms. Pflug-Back said what she said."

The group then moved north, where they attacked a Tim Hortons store, he testified.

Pflug-Back, who could be seen in video and some of the 6,000 photographs of the protest that Hassall took -- several of which were screened for McMahon -- was also dressed in black and had her face covered.

Among the photographs, Pflug-Back, distinguishable by a silver belt with three skulls as a buckle, can be seen hitting a police vehicle window and an ATM screen with a metre-long wooden stick.

Court also saw videos of some of the destruction in which Pflug-Back can be seen taking part.

Under cross-examination by lawyer Steve Gehl, Hassall was adamant he heard Pflug-Back yelling at the Bell and perfume stores, and said the group in front of the window was looking to her for direction.

"I believe they are verbatim comments," he said.

However, he admitted he only wrote down her words several months later, when he was asked to provide a complete statement to police, something Gehl told McMahon made his testimony suspect.

The judge said he believed the officer's account.

After the violence, dozens of protesters, including Pflug-Back, slipped out of their black clothing and donned regular "civilian" clothing, the officer told court.

"Ms. Pflug was the centre of attention during the time people were changing," Hassall said.

The judge discounted that evidence.

During the lunch break, some pushing and shoving occurred outside court as supporters of Pflug-Back used umbrellas to shield her from news photographers and TV cameras.

She retreated back into the courthouse.

The case is one of the few victories for police, who have faced biting criticism for their handling of the tumultuous summit in June 2010.

More than 1,100 people were arrested, most to be released without charge.

Final sentencing submissions will be heard July 13.

The Crown is expected to seek a sentence of 18 to 24 months. The defence wants a conditional sentence.