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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The following table estimates the likely blood alcohol concentration (BAC) after one beer in relation to body weight:
|Weight (in lbs.)
|BAC (as a %)
Blood alcohol content is essentially a measurement of the amount of alcohol in your blood. BAC generally increases as your alcohol use increases.
But note that other factors can affect a person’s BAC. Examples include:
All states impose “per se” DUI laws. These laws say you are guilty of driving while intoxicated if your BAC is above a certain level. Most states use a per se DUI level of 0.08%.
States also impose “excessive” BAC laws, which say that you can receive steeper DUI penalties if you drive with a BAC at an excessively high rate (for example, a rate of 0.15%).
Blood alcohol content measures the amount of alcohol in your blood. For example, a BAC of .20% means that your bloodstream contains two parts of alcohol for every 1,000 parts of blood.
BAC is commonly used in DUI cases when police try to establish whether someone is driving while intoxicated.
Blood alcohol levels are normally expressed as a percentage – for instance .08%. The higher the number, the more alcohol there is in your bloodstream.
BAC can be measured by a:
The number of drinks you consume will have a direct impact on your BAC. Your BAC will increase as you consume more alcoholic drinks.2
But there are other factors, besides alcohol consumption, that can affect a person’s BAC. Some of the more common ones include:
All states and the federal government have per se DUI laws. These laws say you are guilty of driving while intoxicated if:
For example, 49 states follow a .08% per se legal BAC limit. This means if your BAC level is .08% or higher, than you can be arrested and charged for DUI. Utah is the only state where the per se BAC limit is not 0.08% – but rather 0.05%.4
Most states have excessive BAC laws. According to these laws, a judge can impose more severe DUI penalties if you are caught driving with a high BAC.
States, though, tend to vary with regards what an excessive BAC is. For example, in California, a BAC of .15% or higher is deemed “excessive,” and drunk drivers with this level will receive steeper DUI penalties (in comparison to drivers with a BAC under .15%).5
In contrast, Idaho law will also impose harsher DUI penalties for excessive BAC levels. But the law defines an excessive BAC as one above .20% rather than .15%.6
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.