Understanding DUI

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understanding impaired driving

It is not unusual for persons charged with both impaired driving and driving at the legal limit ("at 80") to think they are the same offences and maybe even that proof of one means they will be found guilty of the other.  They are not the same.  For a comprehensive evaluation legal predicament, contact a qualified Calgary impaired driving lawyer.

What is the Legal blood-alcohol (BAC) limit in Canada?

The legal limit for operating a motor vehicle with alcohol in the blood is .08 or 80 milligrams of alcohol in 100 millilitres of blood. Any value “at 80” is illegal according to the Criminal Code of Canada.

How do the police test blood alcohol?

In Canada, blood alcohol is usually tested when the police take a breath sample, but can also be determined via the collection of blood. In Canada, an accused usually does not have the choice as to whether to provide breath or blood; rather, the police make the demand at the time of the investigation.  In Canada, the default position is a “breath sample”.  This is so because taking a breath sample does not represent the same level of interference with the accused’s bodily integrity as the taking of blood. 

What is the difference between Impaired driving and At 80?

Conceptually speaking, the difference between impaired driving and operating a vehicle with blood-alcohol exceeding the legal limit can be summed up as follows: On most occasions impaired driving is proven on evidence that the accused is actually impaired to drive; whereas Over 80 is demonstrated by evidence that shows the accused’s blood-alcohol  (BAC) was at a level equalling the legal limit. It may be that the accused has demonstrated almost no indicia of impairment, but his or BAC is well beyond the legal limit.  Similarly, there are occasions where a person’s BAC is below the legal limit, but they are nevertheless exhibiting serious indicia of being impaired to drive.  For example, I imagine must of us know somebody who can consume a large amount of alcohol but never seem drunk. I am sure most of know somebody who effected by alcohol after only consuming a very small amount (such as one drink). The point is, these two offences are related, but different.

How can BAC be used to prove Impaired Driving (DUI)?

To use BAC as evidence to prove impaired driving, the Crown needs to call expert opinion evidence.  All things considered, this is very unusual for everyday, run-of-the-mill impaired driving cases.  An expert is needed because a trial judge cannot take judicial notice that a person is necessarily impaired to drive just because his or her blood-alcohol exceeded the legal limit (over 80).

The Crown will usually use an expert (a toxicologist) on rare occasions where police have not be able to collect a breath sample or blood sample in a timely fashion.  If the accused has been hospitalized, the police may attempt to seize hospital records or perhaps hospital blood (blood drawn by the hospital). Using records, the Crown may try and have an expert extrapolate from the blood toxicology showing the accused’s ethyl alcohol level at the time of testing to the time of driving.  With a blood sample, the police may have it scientifically testing and have an export extrapolate from the time the blood was drawn to the time of driving. This is a complicated evidentiary procedure that requires assessment by a qualified Calgary DUI lawyer.

For a free telephone consultation with a Calgary DUI lawyer call 403.452.8018.

To learn more about impaired driving, contact a qualified Calgary impaired driving lawyer. Charged with impaired driving, refusing to blow, "at 80" or any other driving offence? David Chow defends cases in Calgary, Lethbridge, Airdrie, Cochrane and throughout Alberta.