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What are your rights during a DUI traffic stop investigation?

Rief Legal How Cases Are Won

During a DUI investigation, it's important to understand that an officer’s main objective is to collect evidence that shows you were driving under the influence. When speaking to you, make no mistake about it: the questions are specifically designed to incriminate you. Some questions will be obvious (e.g., “Did you have anything to drink tonight?” or “When was your last drink?”). But others will be more subtle (e.g., “Where you driving from?”, “When do you last eat?”, or “Do you have any injuries or take any medication?”).


Everything you say is fair game later on at a trial; however, everything you DON’T say is equally fair game. Although you can remain silent during questioning, 12 jurors may interpret your silence as a sign of guilt. Some jurors may feel a simple admission to drinking is less damaging than silence. Remember, it’s not illegal to drink alcohol and drive; it’s only illegal if you were actually under the influence of alcohol (or drugs) while driving.


You have a right to refuse to participate in any of the standard field sobriety tests (FSTs). The most common FSTs are the following:

  • the Horizontal Gaze Nystagmus (HGN) test

    • The officer will ask you to track an object (e.g., a finger or pen) to the peripherals of your vision. If you have alcohol in your system, your pupil, in general, will jerk or bounce at the maximum deviations (like a marble rolling on a unsmooth surface).  

  • the Rhomberg balance test

    • The officer will ask you to tilt your head back, close your eyes, silently count 30 seconds in your head, and then open your eyes and indicate when you've counted 30 seconds. 

  • the One Leg Stand test

    • The officer asks you to stand on one leg, keep your hands to your side, balance your lifted leg 6 inches above the ground, and count outloud (e.g., 1001, 1002, 1003, etc.)

  • the Walk-and-Turn test

    • The officer asks you to take nine steps in a straight line heel-to-toe, then turn around and take nine steps back to the starting point.

  • the Preliminary Alcohol Screening ("PAS") test

    • This is the breathalyzer test where they collect two breath samples of you in the field

    • This test is generally their last FST before arresting you.

    • If you're anywhere near .08%, they're going to arrest you.

The PAS test, which is the breathalyzer test on scene BEFORE you're arrested, is the most important FST for the officers in their investigation. Again, you are NOT required by law to submit to the PAS test, so it's typically wise to refuse to submit to the PAS. However, you do NOT have a legal right to refuse the breath or blood test AFTER you're arrested. In other words, there are two tests—one before you’re arrested and one after. As a condition of having a driving license, every Californian is required to submit to a breath or blood test after being arrested for DUI. If you refuse the second (post-arrest) test, you face further consequences plus officers can force a blood draw, but only if they get a signed search warrant from a judge.


Jurors that hear you refused to participate in the tests may interpret your refusal to participate as guilty behavior. But, that's generally a smaller hurdle to overcome at trial than the incriminating evidence gathered if you do participate. Ideally, it's best to strike a balance where your refusal to cooperate is somewhat excusable (for example, participating in some, but not all tests). 


Remember that whether or not you participate in the tests, the officer will undoubtedly still note that you smelled of alcohol, had red and watery eyes, exhibited slurred speech, and walked with an unsteady gait. That is, regardless of your level of participation, law enforcement will still build the case that you were under the influence based on their observations on scene. And, understandably, they're not going to take chances with safety by letting you drive off if they suspect you're under the influence. Understand that if you refuse to participate, you will be arrested. Participating in the tests, particularly, the PAS test, is a gamble. If you really only had one small drink and you're positive that your blood alcohol is well below .08%, then submitting to a PAS and showing the officer your low blood alcohol level could mean you're sleeping in your bedroom rather than jail or a drunk tank that evening. But, I wouldn't advise that route unless you were absolutely certain that you consumed only a minimal amount of alcohol.

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