A chemical breath test can give a false positive result based on the way that it operates.
Most people are familiar with what happens in a DUI stop. Even if we have never been pulled over or stopped at a DUI checkpoint ourselves, we have seen it on TV or in the movies — a person is pulled over for drunk driving and asked to blow into a breathalyzer. The person is then usually arrested and charged with driving under the influence of alcohol
The first thing to know is that unless you are under the age of 21 or currently on DUI probation, you do not have to consent to take a roadside breathalyzer test (also known as a pre-arrest screening, or PAS). However, you may ultimately take a breath test if you are arrested. So how exactly does a breath test work? How can the police tell if you have been drinking — and how much alcohol is in your blood — through testing your breath?
An experienced DUI lawyer in Pomona, CA will tell you that breath tests are not always reliable, which is why it is so important that your attorney understand how they work to help formulate a strong defense to a DUI charge. Read on to learn more about breath tests and how they are used in DUI cases.
California Breath Tests
California law prohibits operating a motor vehicle if you have a blood alcohol content (BAC) of .08 percent or higher. This BAC limit is lower for some people, such as anyone who is driving a commercial vehicle, on DUI probation or under the age of 21. To prove that a person is driving under the influence of alcohol, the police use their own observations about how you were driving and acting as well as a chemical test of either your blood or breath.
Breath tests do not actually measure the amount of alcohol in your system. Instead, a breath test measures the presence of the chemical compound that contains the methyl group as part of its structure. Because there are thousands of chemical compounds that contain the methyl group other than alcohol, it is entirely possible to have a positive breath test without any alcohol in your system.
As established above, unless you are under the age of 21 or currently on DUI probation, you are not legally required to take a roadside breathalyzer test. However, if you are arrested on suspicion of DUI, you will have to submit to either a chemical breath or blood test. If you refuse to take this test, you will face additional penalties.
If you choose to take the breath test, then you will be asked to breathe into a tube connected to a machine. This machine captures the sample, and then uses infrared spectroscopy to shoot light energy through the sample. Compounds that contain the methyl group will absorb the energy from the light. More energy will be absorbed by your breath sample as the amount of the chemical compound containing the methyl group increases. The machine then determines how much of the light passes through your breath sample to reach the sensor on the other side. Your BAC reading is then calculated based on how much light reaches the sensor.
While breath tests are assumed to be accurate by the general public, but they do not always show the actual presence of alcohol. The test only measures whether a chemical compound containing the methyl group is present — NOT whether that chemical compound is actually alcohol. Substances other than alcohol can contain the methyl group, leading to a false positive breath test result. For example, a person who is diabetic or who suffers from GERD may produce compounds that contain the methyl group — so their breath test results may show a high blood alcohol content even if that person didn’t have a single alcoholic beverage.
A false positive breath test can be challenged by a skilled DUI lawyer. In Pomona, CA and the surrounding areas, contact the Chambers Law Firm at 714-760-4088 or dchambers@clfca.com. We offer free consultations where we can provide a thorough case analysis to help you understand your rights, including the possibility that the breath test results were not accurate due to a medical condition, special diet or other factors.
