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DUI and Probable Cause 101

Probable cause is a phrase you’ll hear a lot in relation to DUIs. At its core, the meaning of probable cause is fairly simple, but it can get complicated when you get into the stages of probable cause required in order for someone to be detained and arrested for a DUI. Learn what probable cause means in a DUI case, and what the stages of probable cause are, in our blog.


What does probable cause mean during a DUI stop?

DUI and Probable Cause


What is probable cause?

Probable cause is a reasonable belief that a crime has been or is being committed. A police officer must have probable cause in order to detain and arrest someone for a DUI.

What are the stages of probable cause during a DUI?

There are 3 stages of probable cause in the DUI process. At each stage, the officer needs to be able to give his or her specific reasons as to what he or she saw that established probable cause. The following are the 3 stages:

Reasonable Suspicion

Reasonable suspicion is what an officer needs to pull you over. This is needed because you’re protected from unreasonable search and seizure under the 4th Amendment. If you commit a traffic violation, then this gives the officer reasonable suspicion to pull you over. You may be speeding, swerving, failing to use turn signals, driving erratically or over the line. Any of these is enough to give the officer reasonable suspicion.

Reasons Why The Officer Suspects You of Driving Under the Influence

Next, the officer needs to establish probable cause to begin his or investigation into a DUI. This means that before the officer asks you if you’ve been drinking or asks you to perform a field sobriety test, he or she needs reasons to suspect that you are in fact driving under the influence. The officer will look for signs that you are intoxicated. These signs include slurred speech, the smell of alcohol on your breath or in the car, visible alcohol containers in the car, disorientation, or glassy, red, or watery eyes.

If the officer sees these signs that you may be intoxicated, probable cause has been established, and they can continue the investigation.

Establishing Probable Cause for an Arrest

The last stage is establishing probable cause for a DUI arrest. Things that give the officer probable cause for an arrest include:

  • You telling the officer that you were drinking or are intoxicated.
  • Failing more than one field sobriety test.
  • Failing a breathalyzer.

If any of these happen, the officer has established probable cause and can arrest you for a DUI.


Bruce Robinson & Associates is a criminal defense law firm based in Baltimore, MD. If you have been accused of criminal actions and need to seek aggressive counsel, Robinson & Associates is here to help. For more information and to schedule your free consultation, give Robinson & Associates a call at 443-524-7395 or visit us at You can also follow us on Facebook, Twitter, and Google+.


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