Breathalyzers and how a criminal lawyer can defend a DUI charge in BC?

Breathalyzers are roadside testing devices used by the police to test for impaired driving, DWI, and DUI without actually extracting something from a suspect’s body. Other tests to determine the blood alcohol concentration (BAC) of a suspected impaired driver involve testing a suspect’s blood, saliva, or urine, all of which are methods that do not yield immediate results.1 By using breathalyzers, police officers can immediately determine whether there is a reason for arrest or not. In British Columbia, if a driver has a BAC exceeding .08 they are legally drunk and cannot be lawfully operating a motor vehicle. When one receives a blood alcohol reading, it is in relation to 100 mL of blood. Therefore if you receive a reading of .04, it means you have .04 grams of alcohol per 100 mL of blood.

Generally there are 3 different types of machines that can test a suspect’s breath in order to determine inebriation. They are called the breathalyzer, intoxilyzer, and alcosensor. All of these devices use different chemical reactions to conclude a BAC reading. It is possible to determine a BAC using one of the above mentioned devices because of alcohol’s incapacity to digest. Unlike other drinks, alcohol is absorbed through membranes in the body, such as the mouth, throat, and stomach. From here it passes directly into the bloodstream where it circulates until it evaporates to the lungs. Once it reaches this point the alcohol passes over the alveoli therefore becoming apparent on one’s breath. Because of this process, these tests are more traditionally referred to as “alveolar breath tests.”² They are no doubt accurate, yet they are a far cry from infallible.

Though testing a subject’s breath is objective and the devices used are accurate, many distortions of fact and procedure can occur rendering a BAC invalid. If your criminal lawyer can prove that the machine used to determine your BAC was not maintained properly, this evidence will be invalid and could likely not be used in court. If the machine is not calibrated correctly and regularly to ensure it is working properly at the time of the test, the result it produces cannot be held as evidence in a British Columbia court.

Another major problem with breathalyzers is that they do not actually identify the alcohol apparent in the blood, yet do so indirectly by measuring the ethyl present in a subject’s alveoli. A different compound called acetone can easily be mistaken by these devices as ethyl, and is present in high concentrations in dieters, or diabetics.

Electrical interferences can also cause incorrect results. Police radios or other electronical devices have the potential to cause electromagnetic interferences compromising the integrity of test results.³

Residual mouth alcohol caused by “burping, belching, or hiccoughing can give high and usually erratic readings because these physical phenomena are all ways in which gas bubble[s] [are] expelled from the stomach."⁴ It is imperative that an accurate breathalyzer test be taken at least fifteen to twenty minutes after the consumption of alcohol. If this is not the case, the inaccuracy of the results can easily be challenged due to alcohol that may still be present in the mouth.

Clearly there are many ways in which a breathalyzer may accuse a sober driver of being impaired, or render a higher BAC than accurate or fair. Since the accuracy of the BAC test is “practically the only contestable issue in most drunk-driving cases” it is important to consider all the issues, and if need be contact a criminal lawyer.

Dykstra & Company are BC criminal lawyers who defend people charged with DUI, DWI, refusing to provide a breath sample (refusing to blow), impaired driving, and other traffic offences.

¹Greenwald. R. 1968. Scientific Evidence in Traffic Cases. The Journal of Criminal Law, Criminology, and Police Science. Vol. 59, No. 1, pp. 57-73
²Spector. H. 1971.Alcohol Breath Tests: Gross Errors in Current Methods of Measuring Alveolar Gas Concentrations. Science, New Series. Vol. 172, No. 3978, pp. 57-59.
³Jacobs. B. 1988. The Law and Criminology of Drunk Driving. Crime and Justice. Vol. 10 pp. 171-229
⁴Greenwald. R. 1968. Scientific Evidence in Traffic Cases. The Journal of Criminal Law, Criminology, and Police Science. Vol. 59, No. 1, pp. 57-73

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