How The Police Determine That A Person Has Been Driving While Impaired

When the police are looking out for impaired drivers (and they are always on the look out for impaired drivers), they watch for vehicles displaying a driving pattern that is out of the ordinary.

They look for a driver who is weaving between the lines, changing lanes without signals, turning without proper signals or just generally driving in a way that looks somewhat different or out of the ordinary. They may stop the vehicle to investigate that kind of driving, and they have the right to do that. The police can stop any vehicle, any time to check to make sure that the insurance and registration are correct, that the driver is properly licensed, and to investigate for potential impaired driving. There are spot checks like RIDE Programs, as well.
When a police officer sticks his head in the car, what he or she is looking for is anything that is out of the ordinary. They will be very alert to an odor of alcohol. They will be looking for bloodshot or watery eyes. They will be listening to speech patterns to see if there is any slurring of the words or very slow or uncertain speech. They will be watching for manual coordination. For example, as you get your driver’s license out of your wallet or you search for your registration and insurance, they will be watching to see if those movements demonstrate any degree of impairment. If the person then gets out of the car, they will watch how they walk, how they stand, whether they seem steady on their feet or are staggering. All those sorts of things are the small clues that the police are looking for to lead them to a conclusion that the driver may be impaired by alcohol or by a drug that is affecting their ability to operate a motor vehicle.
While the law in different provinces in Canada is different, in Alberta the police are not allowed to require drivers to do any form of sobriety test, such as walk a straight line or touch their nose. However, if they have a reasonable suspicion that the person driving the motor vehicle has alcohol in his system, they can demand that the driver supply a breath sample on a Roadside Screening Device. That is a minimally intrusive search and the police officer will usually have such a device in his pocket. It’s a very small, portable breath testing instrument which, when blown into, provides a 3-stage reading: red, yellow, green. Green is a blood alcohol level of less than 50, yellow is between 50 and 100, and red is over 100.
The legal limit is 80, so if you are under 50, clearly you are just going to drive away. If you are between 50 and a 100, the police have an option, and they will most often impose a 24-hour suspension under Alberta traffic law. The police can take away your driver’s license for 24 hours if they find you driving while having consumed alcohol. The upside is that there is no subsequent criminal prosecution or criminal record. There is no long term driving suspension or any of those consequences that flow from a more serious charge. On the other hand, of course, you are not driving for 24 hours. If the result is a red light, over 100, that provides the police with the necessary grounds to arrest the driver and demand that they supply a further breath sample into an evidentiary breath testing instrument like the Intoxilyzer. That person will then typically be charged with both impaired driving and driving with a blood alcohol level in excess of that which is allowed by law.