The theory behind the breath test machine is that it should test air that comes from deep inside the lungs in order to be accurate. The machine tries to prevent a reading that comes from alcohol in the mouth instead of in the lungs. But its ability to distinguish mouth alcohol from lung alcohol is limited if the person did drink some amount of alcohol and thus has some alcohol coming from their lungs. In these cases, mouth alcohol can severely distort the result and make it seem like the person drank much more than they actually did.
The law tries to protect people from these inaccurate results by making officers check a person’s mouth and/or ask a person if they have anything in their mouth. Then, an officer is supposed to watch a person carefully for 15 minutes before they take the breath test. But even if an officer follows these rules conscientiously, alcohol could still end up in the mouth at the time of the breath test. Some possible causes of alcohol in the mouth include:
Because the breath test is testing for small amounts of alcohol in the breath, even a small amount of mouth alcohol showing up in the reading can have a big effect. It is important to describe the events leading up to your arrest and the breath test to a DUI attorney in detail to determine if you may have a mouth alcohol defense.