A Toronto judge has acquitted an 89-year-old peace activist charged after she refused to fill out the 2011 census.

Audrey Tobias says she didn't file her census because it is processed using software from U.S. military contractor Lockheed Martin.

The Crown said Tobias had no lawful excuse for her refusal, which led to the charge against her under the Statistics Act.

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Lawyer Peter Rosenthal had argued that forcing her to complete the census would violate her freedoms of conscience and free expression.

The judge rejected the Charter arguments, but said that her memory and some conflicting testimony leave him with reasonable doubt as to her intent at the time of the refusal.

Judge Ramez Khawly noted that for a conviction both the act and intent of a crime must be proven beyond a reasonable doubt, so he had to acquit her.

"It was an unusual judgment in my view," Rosenthal said outside court. "He described our Charter arguments as hail Mary passes and he didn't catch it...They were novel arguments but he found a more novel argument, it seems, in analyzing the [intent]."

Tobias says the judge put a lot of thought and care into the decision.

"I respect it and I am grateful," she said outside court.

In 2011, StatsCan received 13 million completed census forms, a 98 per cent response rate. Overall, it referred 54 people for prosecution for failing to complete the mandatory census form.