How Residual Mouth Alcohol Affects Breath Test Results

When a law enforcement officer suspects a driver of driving under the influence of alcohol, the officer may conduct a breath test on a Breathalyzer to determine the suspect's blood alcohol content (BAC). Residual mouth alcohol is one of the most common causes of a false positive test result or an elevated result.

In Georgia most police officers carry a portable breath-testing device called the Alco-Sensor.  As covered on our website, the numeric result of the Alco-Sensor is not admissible in our court system.  The Prosecution can only reference whether the result was positive or negative for the presence of alcohol.  The reason the numeric result is not admissible is because of the potential for residual mouth alcohol to affect the result. The Preliminary Breath Test does not have a way to filter out or detect residual mouth alcohol.

The U.S. Department of Transportation and the National Highway Traffic Safety Administration has published studies that show that after a person takes a drink, some of the alcohol remains in the mouth tissues. If the person exhales soon after drinking, the breath sample will pick up some of this leftover mouth alcohol. As a result, the breath sample will contain an additional amount of alcohol and the test result will be higher than the true Blood Alcohol Content. Many things can cause residual mouth alcohol; including most mouthwashes, breath sprays, and cough syrups.

This is exactly why the Preliminary Breath Test result should never be allowed in any court.  However, many states not only allow the result but also penalize people for refusing to take the Alco-Sensor.  Thankfully (for now), Georgia neither penalizes people for refusing the Alco-Sensor nor does Georgia allow its result into evidence.  However, the State is always pushing the envelope, and as a result, we are only one bad appellate decision or one session of the legislature from this being changed.

It takes approximately 15 minutes for the residual mouth alcohol to evaporate from the mouth. Law enforcement officers are instructed to make sure that a DUI suspect has not had any alcohol for at least 15 to 20 minutes before administering a breath test. The problem with this timeframe is that many people worry that admitting they consumed alcohol within minutes of driving will hurt their case. The officer thus administers the breath test too early, and residual alcohol significantly affects the results.

Unlike the Alco-Sensor, if arrested for DUI in Georgia, you are required to take the State-Administered breath test.  Currently, Georgia is switching to from the Intoxilyzer 5000 to the Intoxilyzer 9000.  The manual for both devices clearly says that the officer must wait for 20 minutes before taking the test.  This is because of the residual mouth alcohol issue.

However, Georgia Courts have interpreted “the 20 minute rule” as a suggestion, not a requirement.  As a result, the issue of residual mouth alcohol goes to the “weight of the evidence,” not admissibility of the test itself.  In effect, it's a question for the jury to determine.  Yet juries are not given the entire truth on this issue and assume that if the machine says there was no residual mouth alcohol, then it's not there.  Unless a person can afford expensive expert witnesses, the jury will never hear that the machine does not always properly detect mouth alcohol.

Our appellate courts have gotten this wrong, and it's beyond hopeless.  Our judges fear Mothers Against Drunk Driving (MADD) and public opinion more than they believe in fairness for those accused of DUI. There has always been what many have called the “DUI Exception to the Constitution.”  I call it the “DUI Exception to Common Sense and Fairness.” If the manual says wait 20 minutes, surely there is a reason for it.  It's not a mere suggestion.

Even though the Intoxilyzer has a “slope detector” to detect a spike in the reading caused by residual mouth alcohol, it's an imperfect solution.  Why not just wait the 20 minutes to actually make sure the person is getting a fair test?  It's only 20 minutes, and that 20 minutes can even include the time on the way to the jail.  It's 20 MINUTES!!

If you have been arrested for DUI and you submitted to a breath-test, act now.  You only have 30 days to have your Georgia DUI attorney file an appeal to save your driver's license.  Atlanta DUI attorney Richard Lawson is a former DUI prosecutor with over 20 years experience defending people accused of DUI throughout Metro Atlanta and DUI in North Georgia. Call 24 hours a day, 7 days a week.  We are here when you need us most.