San Rafael attorney Paul Berglin says, "Breath alcohol testing is very sensitive."
Berglin does not advocate drinking and driving, but he has seen clients wrongly accused and in some cases, it is as simple as what is on your breath.
"They may regret that their car was impounded, and they were arrested, and they were subjected to the humiliation of being booked in a jail, and forced to take their jewelry off, and their clothes off," he says.
"Some of the breath sprays like the Listerine breath sprays, the carrier liquid in those is actually alcohol," explains Kenton Wong with Forensic Analytical Sciences in Hayward.
They have seen cases thrown out of court because people accused of drinking and driving had used products containing alcohol including cough syrup, cold medicine, mouth wash even lip balm.
"When an individual consumes an alcoholic beverage, some of that alcohol is immediately absorbed into the lining of the mouth," Wong says.
That alcohol also shows up on field breath monitors, commonly called breathalyzers.
"I wouldn't necessarily characterize it as a false positive because it is alcohol and it is in your system," says Tony Tam with the California Highway Patrol.
Law enforcement says that the breath tests are just one of the tools that help an officer determine whether someone is drunk.
"It helps the officer to form on an opinion on whether someone's impaired," Tam says.
Police are supposed to watch a suspected drunk driver for 15 minutes before giving the test, but in many cases they do not. Even a simple belch can throw off test results. Results higher than the .08 legal limit will land a driver in jail, where they would then be required to submit to more elaborate breath or blood tests in custody.
ABC7 legal analyst Dean Johnson says, "A breathalyzer test may show that you are under the influence when you're not, it may fail to show that I'm under the influence when I am."
Johnson offers this advice to anyone who thinks they may have been wrongly accused.
"Get a good lawyer," he says. "One who understands that a DUI is a serious matter and that involves serious scientific issues."
If you are unsure of your blood-alcohol level, do not drive. You can test yourself. The personal breathalyzer market is rapidly growing and they go for about $300.
Research shows the market is currently worth more than $215 million, up from roughly $28 million in 2005.
Written and produced by Ken Miguel.