California’s DUI laws can be complex and confusing. In this section, our attorneys break down the rules and explain the process.
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DUI breath testing machines detect alcohol about 24 hours after you consume your last drink. Though if you metabolize alcohol quickly, it is possible a breathalyzer will not detect alcohol after 12 hours.1
Factors that influence the speed at which your body metabolizes alcohol include:
As to the last two factors, keep in mind that you will likely metabolize alcohol at a slower rate as you grow older. Further, males generally tend to metabolize alcohol at a faster rate than females.
The smell of alcohol can linger on your breath for 12 to 24 hours after consuming your last drink.3 Therefore, police who smell alcohol on your breath during a traffic stop may suspect you of drunk driving when in fact it has been hours since your last drink.
Note that alcohol on your breath is usually not enough evidence, on its own, for a police officer to arrest you for DUI/DWI. Police make their determination after:
A breath test calculates your blood alcohol content/concentration, or your BAC.
You will usually see blood alcohol levels expressed as percentages. As the percentage increases, you will have a higher BAC.
Note that 49 states say you are guilty of drunk driving if you have a BAC of .08% or higher. Utah is the only state where the legal limit for a DUI is .05%.4
In some states, commercial drivers commit DUI by driving with a BAC of .04% or higher. Meanwhile, under-21 drivers can usually be arrested with a BAC of only .02%.
When you drink alcohol, it travels through your digestive system and into your small intestine. The alcohol then diffuses into your bloodstream.
Once in your blood, the alcohol circulates throughout your body and eventually reaches the capillaries in your lungs. That is why some alcohol gets released when you exhale.
After you exhale into a breathalyzer, the machine takes your sample and measures your “BrAC,” short for breath alcohol content. Then it converts this BrAC number into a BAC number (short for blood alcohol content, as discussed above).
If you are arrested for drunk driving, you typically have the choice between taking a breath or blood test. Blood tests can detect alcohol for up to 12 hours after your last drink.
Note that a urine test can detect alcohol for up to five days after your last alcoholic beverage. Finally, a hair follicle test can detect the presence of alcohol for up to 90 days after alcohol consumption.5
For more in-depth information, refer to these scholarly articles:
A former Los Angeles prosecutor, attorney Neil Shouse graduated with honors from UC Berkeley and Harvard Law School (and completed additional graduate studies at MIT). He has been featured on CNN, Good Morning America, Dr Phil, The Today Show and Court TV. Mr Shouse has been recognized by the National Trial Lawyers as one of the Top 100 Criminal and Top 100 Civil Attorneys.