What is the Difference between "Impaired Driving" and "Over 80"

A common question among those charged with drinking and driving offences is “What’s the difference between “impaired driving” and “over 80”?” The answer is that while these offences are clearly related to one and other, the key distinction is how they are proven in court.

“Impaired driving” is an offence under section 253(1)(a) of the Criminal Code. This section makes it an offence to operate or be in care and control of a motor vehicle while impaired by alcohol, or a drug, or a combination of alcohol and a drug. Whether or not you are driving while impaired is not determined by your blood alcohol concentration, though this may be a relevant consideration that a judge can weigh in assessing whether or not you were driving impaired, presuming that toxicology evidence is lead to support this inference. Impaired driving allegations are generally proven through evidence of poor driving, for example weaving in your lane, evidence of a car accident, driving excessively fast or excessively slow, etc., and/or through evidence of impairment of your motor skills and co-ordination, for example slurred speech, stumbling or staggering while walking, swaying while standing, difficulty in following instructions, etc. Where it is reasonably believed that a drug may be contributing to a person’s impairment, a demand for a drug recognition evaluation can be made. Following a drug recognition evaluation, some subjects will be required to provide urine samples which can then be used to demonstrate the presence of a drug in the person’s system to support an inference of impairment. Importantly, a person can be impaired by alcohol while still having a blood alcohol concentration that is below the legal limit. Most toxicologists will tell you that for many people, impairment of one’s ability to operate a motor vehicle begins at a blood alcohol concentration of just 15mg of alcohol in 100mL of blood. The legal limit is 80mg of alcohol in 100mL of blood. So you could be impaired and be at less than 20% of the legal limit. The flip side to this is that most, but not necessarily all, people will be impaired if their blood alcohol concentration exceeds the legal limit of 80mg of alcohol in 100mL of blood. Another important point to note is that you can be impaired by legal prescription medication. This is particularly true when prescription medication is combined with even just a small amount of alcohol consumption. The leading case on impaired driving is R. v. Stellato, [1994] S.C.J. No. 51, which states that proof of even slight impairment of driving is sufficient to prove impaired driving under section 253(1)(a) of the Criminal Code. However, it is important to note that impairment must be proven beyond a reasonable doubt in a criminal court. Thus, R. v. Stellato stands for the fact that proof of slight impairment of driving is sufficient, but it does not stand for the notion that slight proof of impairment of driving is sufficient. Therefore, allegations of impaired driving can often be challenged by showing an alternative explanation for the driving conduct observed or by showing that the officers’ observations of “impairment” are inconsistent with the video evidence in the case, just to name a couple of defences.

“Over 80” is an offence under section 253(1)(b) of the Criminal Code. This section makes it an offence to operate or be in care and control of a motor vehicle with over 80mg of alcohol in 100mL of blood. This is what your breath test results are primarily used for, proving the “over 80” offence. This offence is far more technical in nature than the “impaired driving” offence. A person cannot tell the difference between when their blood alcohol concentration is 75mg of alcohol in 100mL of blood and when it is 85mg of alcohol in 100mL of blood, yet there is a big difference if you are considering taking a drive. In order to prove this offence, the Crown prosecutor has to present admissible evidence of your blood alcohol concentration at the time of driving. This is somewhat challenging, as your blood alcohol concentration is not measured at the time of driving, but only later at the police station (or mobile RIDE unit). They show your blood alcohol concentration at the time of driving by relying on the “presumption of identity”, which allows the judge to conclude that your blood alcohol as measured at the station is accurate to the time of driving, provided that a number of preconditions are met. These cases can be defended by undermining the preconditions required for the “presumption of identity” to apply, or by bringing an application to exclude your Intoxilyzer results from the evidence, just to name a couple of potential defences.

Most often, people will be charged with both “impaired driving” and “over 80”, but you can be charged with just one or the other of these offences, depending on the nature of the evidence. However, given the overlap between these offences, if you are charged with both of these offences, you cannot be convicted of both (due to the rule from Kienapple v. R., [1975] 1 S.C.R. 729.).

So what is a safe amount of alcohol to consume and still be able to drive? Well you may not like the answer, but according to the toxicologists that we have worked with, there is no safe amount of alcohol to drink if you plan to drive.