A per se law in a DUI case means that once a person is tested and is found to have a blood alcohol concentration of 0.08 or higher, no other evidence is needed to show that the person was intoxicated by law. In the United States, every state follows this rule, and if you are stopped with a BAC of 0.08, no other evidence will be needed to charge you with driving under the influence.
Does this mean that I can’t defend myself?
Even though the police need no other evidence, that doesn’t mean your case is a lost cause or that you’ll be facing a conviction. There are still ways you can defend yourself against the charges. For instance, if the officer had no reason to stop your vehicle, then that could result in the case being dropped. You can also question the validity of test results and the accuracy of the machines used to get those results.
Are there per se laws for driving while intoxicated by drugs?
Driving under the influence of drugs is slightly different, although there are some per se laws that apply in a handful of states. Virginia has a zero-tolerance policy. The laws that apply to a DUI can’t be applied in the same way, because there aren’t any straightforward field tests that can be used to show a person is drugged and driving.
While the officer can prove you appeared intoxicated, unless a test comes back positive, there may not be enough evidence to convict you. You may be able to challenge the findings if they do come back positive, too. Drug analysis can still be challenged, because some drugs stay in your body days, weeks or even months after you’ve stopped taking them.
Source: FindLaw, “Per Se DUI Laws,” accessed June 09, 2016