The Supreme Court of Canada building in Ottawa, Ont. (JOHN MAJOR/QMI AGENCY, file)

The Supreme Court on Friday ruled that forcing an accused drunk driver to prove that a breathalyzer is defective is constitutional.

Under tougher rules introduced by the Conservative government in 2008, it's more difficult for an accused drunk driver to question breathalyzer results -- they must prove the breathalyzer was defective or that it was used improperly in such a way that the results can't be trusted.

In a 5-2 ruling, the top court determined the law is a reasonable violation of the right to be presumed innocent until proven guilty.

The decision stems from the case of Anic St-Onge Lamoureux, a Quebec woman who was arrested in 2008, charged with impaired driving and found guilty.

Defence lawyer Julie Bolduc told QMI Agency the law puts the burden on the accused to prove they're not guilty, which runs counter to Section 11(d) of the Charter of Rights and Freedoms -- the right to be presumed innocent until proven guilty.

The Supreme Court agreed the new rule violates that constitutional right but determined it's justified under Section 1 of the charter because the law "violates the right to be presumed innocent as little as reasonably possible."

Federal Justice Minister Rob Nicholson said in a statement he was pleased by the ruling, which he said would limit an accused impaired driver's defence "to only cases where there is also evidence of either equipment malfunction or operator error."

-- With files from Valerie Gonthier