VANCOUVER -- The B.C. Supreme Court ruled Monday that a government report on breathalyzers is not admissible when reviewing a roadside ban.

The judgment said that not only is the document known as the "Superintendent's Report on Approved Screening Devices" inadmissible according to the Motor Vehicle Act, an adjudicator who based her decision to uphold an Immediate Roadside Prohibition on the report was also mistaken.

According to court documents, Angela Lichun Buhr was asked to take a breathalyzer test in February, when a police officer pulled her over at about 2 a.m. after "a report was made of erratic driving."

Under B.C.'s drunk driving law, police officers must tell drivers they can have a second test if they fail the first one, and the lower of the two readings will prevail.

Buhr took two tests, and while one showed a fail reading, the other did not register, said the court documents.

The temperature of the second device -- an Alco-Sensor IV DWF -- was nine degrees Celsius at the time, according to the officer who issued Buhr the roadside ban.

Buhr challenged the driving prohibition, court documents say, and at her review hearing, her lawyer pointed to the breathalyzer's manual, which stated that a reading cannot be initiated if the approve screening device's temperature is below ten degrees, or above 40 degrees.

Court documents show the adjudicator upheld Buhr's driving ban, pointing to a government report that says while an approved screening device can be inaccurate when outside the ideal temperature range, a test can still be completed.

"I note there is no indication in the evidence before me that the actual functionality of an ASD is affected by its temperature; rather only its accuracy may be affected," said the adjudicator's decision.

"So, even though the second ASD was operating at a temperature outside of the optimal range, and you had successfully produced a second breath sample, its accuracy may have been reduced, but any reduction in its accuracy would have been in your favour."

But Justice Richard Goepel said in his ruling on Monday that the government report is inadmissible according to the law. An adjudicator's considerations are only limited to the statements or evidence submitted by the driver, and any documents or information forwarded by the officer who handed out the driving ban, he said.

"On this ground alone, the prohibition must be quashed," he said in his ruling.

Even if the report was admissible, Goepel said he would have overturned the driving prohibition anyway because the adjudicator failed to consider the breathalyzer's instruction manual.

"That finding is clearly in error," said Goepel. "The Adjudicator had before her evidence that an approved screening device would not operate below 10 degrees Celsius."