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How do the police establish probable cause for DUI?

On Behalf of | Apr 28, 2023 | Criminal Defense |

If you are pulled over for DUI, you may want to be sure the police had a legal basis for their action. After all, the 4th Amendment protects you from unlawful arrest on flimsy grounds. In other words, law enforcement must satisfy the legal standard of reasonable suspicion to initiate the stop. And even after the stop, they must have probable cause to arrest you. 

If the police stop, investigate and arrest you without probable cause, you may cite this as a defence during your DUI trial. So what is probable cause and how is it established in a DUI case?

Understanding reasonable suspicion

Basically, reasonable suspicion is used to determine law enforcement’s decision to perform a search. In the context of drunk driving, the police must be reasonably suspicious that you are intoxicated based on your driving behaviour. This can include erratic driving, ignoring basic traffic signals, hugging the centreline or driving with your lights off at night. 

Based on your driving behaviour, law enforcement may pull you over. However, they cannot arrest you unless they obtain further evidence that you are drunk behind the wheel. And this is where probable cause comes in.

So what leads to probable cause?

Before the police can arrest you for drunk driving, they must have probable cause to do so per the provisions of the Fourth Amendment. Probable cause means that law enforcement not only has a suspicion that you have or are committing a crime, but that they also have actual knowledge that you have committed the crime or that you are in the process of doing so. 

In the context of drunk driving, the police will have probable cause that you are drunk driving if, upon the stop, you fail the breathalyser test. And if you refuse to take the chemical test, the police can still rely on your driving pattern, odour or presence of alcohol in the car and slurred speech to establish probable cause. 

Protecting your rights

Being charged with drunk driving is a big deal. Learning more about your constitutional rights can help you build a strong defense should you be charged with drunk driving.