Duhaime's Law Dictionary

Impaired Definition:

A deterioration of an individual’s judgment and decrease in his or her’s physical ability. Used primarily in criminal law; driving under the influence of alcohol or disability law in regards to a person’s physical or mental impairment.

Canada’s Criminal Code prohibits the driving or operation of a motor vehicle (car, truck, boat, snowmobile, aircraft, train or other) while that person’s ability is impaired by alcohol (§253):

“Every one commits an offence who operates a motor vehicle or vessel or operates or assists in the operation of an aircraft or of railway equipment or has the care or control of a motor vehicle, vessel, aircraft or railway equipment, whether it is in motion or not, while the person’s ability to operate the vehicle, vessel, aircraft or railway equipment is impaired by alcohol or a drug; or having consumed alcohol in such a quantity that the concentration in the person’s blood exceeds 80mg of alcohol in 100ml of blood.”

A person can be so inebriated that he or she is unable to operate a vehicle; total impairment. Others, are below their normal ability to function: impaired.

A breathalyzer provides evidence of impairment to drive a motor vehicle but there are many other ways to prove impairment.

In R v McKenzie, as far back as 1955, the Alberta Court observed that:

“There appears to be no single test or observation of impairment of control of faculties, standing alone, which is sufficiently conclusive. There should be consideration of a combination of several tests and observations such general conduct, smell of the breath, character of the speech, manner of walking, turning sharply, sitting down an rising, picking up objects, reaction of the pupils of the eyes, character of the breathing.

“If a combination of several tests and observations show a marked departure from what is usually considered as the normal, it seems a reasonable conclusion that the driver is intoxicated with consequent impairment of control of faculties and therefore that his ability to drive is impaired.”

drinking and drivingRelying in part on R v McKenzie, the Quebec Court of Appeal, in R v Laprise, wrote, in 1996:

“The impairment of one's ability to drive is generally understood as meaning the alteration of one's judgment an decrease in one's physical abilities.... (T)his impairment does not need to reach an particular level. (T)he burden of proving guilt beyond a reasonable doubt is met when proof is made that the accused's ability to drive an automobile was impaired by alcohol or a drug, and nothing further is required. What Parliament requires ...  is a finding of impairment of one's ability to drive and not a "marked" impairment.

“In order to establish that the driver was impaired, the Crown has available very varied means of proof. First of all, it can adduce evidence, through the testimony of a police officer or any other person, of the characteristics of the accused's driving.

“His condition can also be inferred from the usual observations, such as the smell of alcohol, unsteadiness on his feet or glassy eyes.

“This may also be demonstrated using the results of breath, urine, or blood test....

“Finally, other tests such as the ability to walk a white line, sometimes permit the inference that the driver is impaired.”

The Saskatchewan Court of Queens Bench, in 1997 (R v Landes) set out a similar list of tests typically used to determine impairment for the purposes of operating a motor vehicle:

“An opinion as to impairment, be it by the trial judge or a non-expert, must meet an objective standard of "an ordinary citizen" or a "reasonable person" in order to avoid the uncertainties associated with subjective standards particularly when based on inferences. To that end a list of tests and observations has been developed for use by peace officers and courts in determining whether an accused's mental faculties and physical motor skills were impaired by alcohol to the degree of impairing the accused's ability to drive a motor vehicle.

“Those observations and tests include: (1) evidence of improper or abnormal driving by the accused; (2) presence of bloodshot or watery eyes; (3) presence of a flushed face; (4) odour of an alcohol beverage; (5) slurred speech; (6) lack coordination and inability to perform physical tests; (7) lack of comprehension; and (8) inappropriate behaviour.”

To this must be noted the cautionary judgment of the Alberta Court of Appeal in a 1996 case R v Andrews in which Justice Conrad wrote:

“(A) conviction on a charge of impaired driving can be founded on proof beyond a reasonable doubt of slight impairment of the ability to drive. If the ability to operate a motor vehicle is impaired (even slightly) by alcohol or drugs, it is not necessary that the degree of that impairment be marked.

“The courts must not fail to recognize the fine but crucial distinction between slight impairment generally, and a slight impairment of one's ability to operate a motor vehicle.

“Every time a person has a drink, his or her ability to drive is not necessarily impaired. It may well be that one drink would impair one's ability to do brain surgery, or one's ability to thread a needle....

“(J)udges must be careful not to assume that, where a person's functional ability is affected in some respects by consumption of alcohol, his or her ability to drive is also automatically impaired.”

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