Mouth alcohol" refers to the presence alcohol in the mouth when a breath test is being administered. Mouth alcohol can cause an abnormally high breathalyzer test result, but actually quantifying it is difficult. A breath test result will show higher than normal results if the suspect has mouth alcohol.
There are many factors that can cause mouth alcohol, a few are:
Breath fresheners do have trace amounts of alcohol. Products such as Listerine and Binaca contain small levels of alcohol and can certainly affect breath test results. Cough medicines such as NyQuil also contain alcohol and can affect test results the same way.
Bodily functions such as hiccups, burps, or even vomit can also affect the test results. Actions such as these bring the vapors of alcohol from the stomach back up to the mouth.
A hiatal hernia can also cause elevated test results.
Dental caps and bridges can capture alcohol in a crevice and be blown out by a breath.
If the suspect has a chronic reflux condition, alcohol can travel up from gastric distress.
This is why Title 17 of the California Code of Regulations requires that a law enforcement officer observes someone for 15 minutes prior to administering a breathalyzer. If a person vomits or burps during the 15 minute period the officer is supposed to begin observing for another 15 minutes. If law enforcement officers do not comply with Title 17 requirements the accuracy of the test can often be successfully challenged.
I will need to do a thorough review of the timing of the drinking and the timing of the breathalyzer test to evaluate how accurate the breathalyzer test result in a given case is. I also typically subpoena records of the specific breathalyzer device to ensure it was properly calibrated and review the maintenance records.