The British Columbia Court of Appeal has attempted to provide guidance on the distinction between using signs of impairment at roadside to form grounds for a breath demand versus using signs of impairment at roadside as evidence of impairment at a later impaired driving trial:
Para [69] A helpful way to apply the rationale of these decisions might be for a court first to determine the investigating officer’s focus or purpose at the roadside stop. If the evidence establishes that the officer formed the opinion from his or her initial interaction with the motorist, that it was necessary to remove the driver immediately from the road for safety reasons, then the investigator’s observations of the driver made thereafter would be available at trial to prove guilt on a subsequent criminal charge: Chand. However, if the evidence establishes that the purpose of the investigator’s direction to a motorist to exit his vehicle was to determine whether grounds existed to make a breathalyzer demand, then the observational evidence obtained thereafter would not be available to prove the guilt for a criminal offence: Milne. This might be a fine distinction but I would suggest an intelligible one. R. v. Visser, 2013 BCCA 393