You had a couple drinks with your friends, but you think you’re good to drive. As you are driving home, however, you get pulled over by a police officer. Just your luck.

You are sure you were driving safely, why did they pull you over? Does this mean you will be arrested? Whether or not you are taken to jail depends on if the officer has probable cause to believe you were driving under the influence of alcohol. But what does probable cause mean?

Reasonable suspicion or probable cause?

In order to pull you over for DUI in the first place, the officer needs to have a reasonable suspicion that you are driving under the influence. In order to make an arrest, they have to have probable cause. While it may seem like semantics, there’s a distinct difference between the two:

  • Reasonable suspicion is simply when an officer thinks you committed a crime.
  • Probable cause is when the officer has enough evidence to believe you most likelycommitted a crime.

Reasonable suspicion can arise from you simply drifting out of your lane. In order to have probable cause, which can come from a field sobriety test or even the smell of alcohol on your breath.

Do you have to take a sobriety test?

The most common method an officer has of proving your guilt is through a sobriety test. But there are two primary types of tests: a field sobriety test and chemical sobriety tests.

Field sobriety tests are used to establish probable cause, before the arrest. These can include a preliminary breathalyzer test, a “walk and turn” test or a “one-leg stand” test. These tests are often unreliable, and you can refuse to take them. This may not stop the officer from finding probable cause to make an arrest, however.

Chemical sobriety tests are the breath or blood tests taken after arrest, and are used to get an accurate reading of blood alcohol content at the time of arrest. You cannot refuse these tests without penalties under California law.

Ultimately, when you are pulled over for suspicion of drunk driving, be aware of your rights and don’t give the officer any probable cause to arrest you. They cannot arrest you on a hunch, and if they do, it may hurt their case against you.